BOLTR: 2 Stroke Engine.

We use a boroscope to quickly troubleshoot a 2 stroke engine and then we take it apart to see how it works. Considering these things are 2 for a dollar, they are testament to modern engineering and the power of "economies of scale".
Small engine mechanic; a channel worth checking out! / donyboy73
Long term projects here: / ave
Easter egg: • Video

[@DJ_Dett]

Best power mixes are usually something like 12:1. The Stoichiometric ratio for optimal fuel burning is about 15:1. The problem with the 15:1 mixture is that it burns much hotter because of the more efficient mixture, which can lead to preignition and detonation. With a richer mixture, the fuel will burn slower (giving a longer push time) and some of the fuel is used to transfer heat. That problem where the engine starts to run away and then blows up is when you start hitting that 15:1 ratio. It gets hotter and the bang is banging faster until the fuel is detonating, giving you a pinging sound. Let it get bad enough, and you'll get preignition (which is where the fuel detonates early). The piston wants to go up, the bang wants to go down, and the connecting rod says "fuck this, I'm out".

[@mareklehmann293]

15:1 is decent, at idle the etec engines in skidoo run around 26:1 mid range RPM are running about 19:1, but because the combustion is so computerised it controls it so you dont detonate. I witnessed this first hand on my Turbo etec which at full RPM would still pull 13.1:1. First time i saw the numbers on my AFR gauge i nearly had a heart attack. Goes to show you what technology can do :)

[@pierreburton4523]

Finally, the right answer. I believe most gas powered cars aim for 14.7:1. Anyways, yes. If you tune a lot of small engines like I do, you can do it by ear, or using a tach and hear when it starts pre-detonating, as the RPM's will start to drop again, as if it's too rich. Anyway, we always err on the side of too rich. Diesel is a different beast and can be leaned WAY WAY out without getting dangerously hot. All those guys up there saying that it's because the fuel is used for lubrication, or because the piston get's hot and expands into the cylinder wall.... oh my goodness. Or that other guy talking about tuned pipes.... LOL.... literally nothing to do with why engines blow themselves up.

[@evanleebodies]

Can't you mitigate pre detonation by adjusting the ignition timing?

[@joshuavoss4354]

evanleebodies ah no since your predetonation is a detonation not caused by your spark plug. it's usually cause by too high of pressure or to hot of engine temperatures or even sometimes a combination of the two.

[@totherarf]

There is no way to adjust the ignition timing! The spark is caused by the breaking of a magnetic field created by the magneto which is connected directly to the flywheel and crank! Pre-ignition (pinking) is usually caused by the carbon deposited on the cylinder head and piston getting hotter than the flash point of the fuel. As soon as the fuel hits the carbon it ignites so the spark is not the cause! There re other 2 stroke engines that have points which are opened by a cam on the crank so allow for adjustment!

[@SquillyMon]

As a mechanic, I know this material front to back, left to right and also outside the box. Most of my learning takes place when AvE talks about "Electrosity and Angry Pixies".

[@shurdi3]

I like to imagine that AvE has a focus puller who he just verbally abuses

[@SANDSCORCHER]

😆👍🏻

[@stevenmitchell9250]

Focus you f**k! 😄

[@imJaymo]

I always feel like I learn more from your vi-jay-ohs than I did from taking engineering classes.

[@806luck003]

First of all, my favorite BOLTR yet. Now, to answer your question, like everyone else has said, the 2 stroke engine is set up to run super rich compared to a 4 stroke. This is because it gets not only it's lubrication from the fuel mixture, but it also gets added cooling from the fuel/oil mix when it runs rich. It is running richer than the ideal fuel air ratio for added cooling. When you get an air leak (more air) it goes from overly rich to closer to the ideal fuel/air ratio therefore it runs like hell... until it seizes from overheating (due to not having the added cooling from the rich fuel mixture). The piston heats up, expands, and grinds into the cylinder wall and seizes.

[@806luck003]

Also.. DO MORE ENGINE SHIT!!!

[@TractorWrangler01]

Awww.. I was going to tell him...

[@julietbranco1505]

so why does it also happen with four strokes? Riding motorcycles has taught me that when the satisfaction factor suddenly spikes, it's time to turn the tank valve to Res and find a gas station yesterday.

[@TractorWrangler01]

+Juliet Branco Because you can't run an engine lean like that constantly. It creates an environment inside of the combustion chamber that has a negative effect on engine reliability. The newer fuel injected engines try to address these problems to obtain higher fuel mileage but there is only so much you can do with the technology we have without running up the cost to the consumer beyond the price that they can pay. Therefore 4 stroke engines still run a bit rich.

[@coast2coast00]

4 strokes also use the fuel to cool the cylinder. Although they will run great at the perfect ratio, they will run too hot and damage the engine.

[@indiglowpufferfish1002]

Aircraft Mechanic here. Air cooled engines are generally set to run rich. It is done this way because the fuel helps with cooling. When you run an engine a bit rich you are not getting full power however you get the benifit of added cooling. So when the seal springs an air leak. This is in effect leaning the Fuel air mixture causing the engine to get closer to that stichiometric value. This allows for more bang. Aka. POWA. However this is where the trouble comes in. The cooling benifit of running rich is no longer in effect. So bad news. Things start getting hot, Your engine goes Boom boom cachoo and you find yourself off in the big old blue with an extra anchor. Hope this helped. (If you want to know more grab an aircraft powerplant book. The FAA is still back in the 1900's. So much of general aviation is a few gen's old as far as engines go. It will run you through all of it.)

[@Rhino90_au]

100% correct Sir! I didn't see your reply and wrote basically the exact same thing.

[@marksmith6837]

Teledyne Continental approves of operating " lean of peak" cylinder head temps in cruise. Set your power, lean mixture to peak CHT, lean mixture more till CHT falls off. Effectively air cooling with a super lean mixture. Does it work? Yes. Is it good? Manufacturer says ok. As an aircraft mechanic do I like it?. Yep, keeps me busy doing top ends.

[@Adam-bw4lw]

+Mark Smith WELL.....LOL😂

[@scarob995]

A&P student, was looking to say this same thing! This is the answer you're looking for AvE.

[@TheApothecaryAus]

All i remember from my course was.... "CONVERGENT DIVERGENT DUCTS".

[@bill6590]

This is one of the best explanations of a 2 stroke engine I've ever seen or read. It should be shown to all budding mechanics. Great job, great show: keep them coming.

[@danm1026]

There aren't actually any budding mechanics. It's a dead dark art lol

[@elena6516]

@@danm1026 it's all "flash the ecu" now

[@Jackofafewtrades]

@@danm1026 I'm a wannabe deadbeat budding mechanic so there's hope.

[@danm1026]

@@Jackofafewtrades hope springs eternal. My best advice is this: be organized with your parts use boxes bags for bolts with labels and in your diagnostics be methodical. Has taken me places.

[@franciscodanconia45]

If I had seen this like twenty years ago I’d still have one of my leaf blowers... I might have tried to fix it instead of throwing it over the fence...

[@ncrdisabled]

As you may know I am a disabled vet no legs . In a wheelchair. But some days I get lucky . I go to yard sales when I can . I bought a stihl fs 45 for 10 bucks . The lady was selling things found in the garage after her husband passed away . She told me it did not run right so her husband just put in the garage and did not take it back due to he was getting sick. I think she gave me a discount because I was in a wheelchair. I got it home opened it up found from the factory they had put a fuel filter in the wrong way causing it not to run right. You should see me doing my yard in my wheelchair !!!!!

[@carsonp.7009]

man that sure was a stihl of a deal!

[@DeliciousDeBlair]

Sthihl Wheels... (~_^)-b

[@blindabinda1234]

Nice find man. Keep up the good work. If only kids these days would have half of the ambition you do I might be able to find a good laborer.. haha take care man and keep on going. You are a true inspiration

[@LasseJOugaard]

Ah! The everlasting mythical 2-smoke that goes like the clappers right before it shits it self! That is a constant danger in karting (atleast classic 100cc aircooled karting). As I have understood it, it's a two sided thing. You are completely right, a rich mixture will always, to a certain limit, make more power. Top power is around 12,5:1 Air-fuel-ratio for petrol, stoichiometry is 14,7:1 AFR. The reason a lean 2-stroke goes so well, is a two sided thing. 1 Is the fact that a lean mixture will burn faster than a rich mixture, regardsless of the fact that the rich mixture will make more power / torque. As the rpm increases the lean mixture is needed to make the flame-front move fast enough to keep up with the piston. As a gokart (and a moped for that matter) usually is a single speed transmission, more RPM means that you can chooch faster down the straight than the other guy. 2 The other part of this is the fact that a lean mixture burn a LOT hotter. Hotter action, means hotter components (yeep...) and therefore greater thermal expansion. Now I'm pulling on my experience in gokarts again; In 99% of engines the pistion is aluminium (with an I! ) and the liner is cast iron (inside an alu cylinder). Therefore the hotter it gets, the smaller the piston-to-cylinderliner tolerance gets, because the aluminium piston expands more. The smaller the tolerance, the better the engine seals, and hence more of your suck-squeeze-bang-blow goes to chooch you down the straight, instead of blowing by the piston. This is also where the failure comes into play. A gokart engine is gapped at 0,1mm piston-liner. As that aprroches 0, the friction and heat becomes immense, eventually melting the piston - partying inside the engine ensued... That's the point where it goes *waaaaaaah- klonk* and you find yourself going 100km/h with locked rear wheels. Fun fact - in gokart engines we try to combat this with skoog-em oil-fuel-ratios and oil types. We run the oil 16:1 (yep, 6.25%) and only oil with good 'ol 'murican castor beans in it, as castor oil has more stable properties at very high temps. It also makes residue with extra cancer, and a strangely addicting smell as a free bonus. Hope this helps AvE - keep up the juicy "vid-jay-ohs"!

[@RenaxTM91]

this gave me a idea: If your in the final of a important race, in the last lap, right behind the leader. can you cheat this? Make a hole/pull out a plug and go faster in the last straight, win the race by sacrificing the engine? ofc it has to be timed right, and you run the risk of finishing with locked rear wheels, going sideways in a deathtrap, but you might gain a advantage?

[@LasseJOugaard]

Hmm, a hole / plug wouldn't work. But we do have slang term called "Carburetor Chess". Effectively you can do what you say, by leaning out the mixture with the needles. The needles AvE mentiones here, can be tuned with finger screws on a kart. Leaner will give more RPM and more top speed, but you risk killing the engine.

[@806luck003]

+Lasse J Ougaard I have to respectfully disagree with your statement that "rich mixture makes moar powah". Wrong. A two stroke is set up to run overly rich for added lubrication and cooling. When you get an air leak, it simply leans out the air/fuel ratio and puts it closer to the ideal ratio for maximum power. At this ideal ratio for power, you are no longer at the ideal ratio for fuel cooling and lubrication, and the engine seizes. A two stroke runs a rich inefficient mixture by design. When you lean it, it runs more efficiently, but it loses critical cooling and lubrication.

[@MikeDawson1]

@Clorox Bleach: I think this is the answer AVE is looking for

[@LasseJOugaard]

@Clorox Bleach That might actually well be the case - the principle of what I said holds true though. Leaner mixture burns faster, the "window" of AFR is just different to what I thought. I know modern laptimers/dataloggers can log Lambda/AFR in karts, but I have no idea whereabout they're running value wise? Im guessing quite rich, like 0,8 ish?

[@samson9428]

Carburetors have always fascinated me. I think it's such a brilliant thing, it's like a computer before computers to regulate a ratio using vacuum and ingenuity. I also think the bigger versions of these that sit between the valve covers of an old truck are fun to tinker with

[@murphyslawperformance]

+AvE from what I understand, the reason a two stroke tends to run really well for a short period of time with a bad crankcase seal is that from the factory, they tune the engines slightly rich to ensure they dont burn up (Lean=hot), so with a small leak they slowly creep up to the perfect air fuel ratio, and then continue to creep past it, engine runs lean, burns hole in piston, and then you walk home

[@setha7781]

Re: Skidoo - In the automotive tuning world, there's an old adage that goes, 'richer is safer, leaner is faster.' You hit the nail on the head when you suggested that additional oxygen allowed in via the crankcase catalyzes the combustion reaction and makes it run like an alarmed hominid until it blows up from spark knock resultant of too lean of an air-fuel ratio.

[@jamesdamico8899]

The air leak leads to more power because you are actually getting more complete combustion by putting more air in the crankcase, which then gets sucked into the cylinder. But if you run lean for too long your engine will go to shit and seize, so they are designed to run slightly rich which helps with lubrication. On steam ships we run slightly lean to get more complete combustion, it also helps keep the boiler tubes free of grimey carbon buildup. Plus we don't have to worry about moving parts in the boiler itself.

[@erikverkade3582]

A 2stroke takes of when it's running lean because it starts detonating. The air/fuel mixture gets so lean that is goes from combustible to actually explosive. And the compression starts igniting it way before TDC instead of the spark. And though it runs really clean the brute force of the explosion generally eats your piston right up. If the lack of cooling and lubrication don't get to it before that. As a kid we had more than one dirtbike or moped die on us because we had it running to lean at full throttle. And it would start detonating at high rpm. We liked it because we got more rpm out of it, and when your running 50cc engines you don't look a gifted rpm in the mouth. We just didn't know WE DIDN'T KNOW MAN! This knowledge would have saves us a lot of of money. If you're ever tuning a 2stroke engine you can tell if it's detonating a high rpm by revving it right up unloaded and letting go of the throttle. It should drop right back to it's idle rpm, if it kinda revs in for a bit and drops back down slowly. You can bet your ass it's running lean at full throttle or you're drawing air trough a gasket somewhere.

[@TechBlogOfficial]

Well the answer to your question is actually quite easy. Because of the air leak there is more air in the air/fuel mixture and therefore it runs very lean. The leaner it is the more powerful the combustion is. If you have a very lean mixture then it will expload violently. It's the same principle with gas tanks in cars. Remember this. A full fuel tank is actually safer then a fuel tank that is filled 1/4 of the way because the one with less fuels has more fumes in it and the fumes are what expload not the liquid fuel.

[@danielhaskins519]

Hey I'm not that old of a guy. 27 and I will say I learned a lot growing up by pulling stuff apart. started simple with little 2 strokes like these. I wish the younger generation would pick up on more stuff like this. I think what you do in your videos is great! Hopefully you have a lot of younger subscribers so they can actually learn something.

[@DirtRider500R]

A video I that I can actually understand what yer talkin aboot! To answer your question at 19:50, I first need to really explain how exhaust scavenging works on a 2 smoker. Bear with me, it's gonna be a long read even though it's simplified. Because there's no valves (like a four stroke (yes, I know 2 stroke diesels had an exhaust valve, that's a different application) ), the 2 stroke engine relies on the outgoing and returning exhaust pulses to pull out the exhaust fumes. On the down-stroke of the engine, the exhaust gases flow through the exhaust port while the intake mixture is forced into the combustion chamber. But, because there's no valves, some of that intake mixture flows out of the exhaust port. The piston goes back up, and the cycle repeats itself. HOWEVER, when the engine is in it's powerband (also known as 'on the pipe'), there is little to no loss of intake mixture through the exhaust port! On bigger bore engines (dirt bikes, snowmobiles, etc), there's an 'expansion chamber' that makes use of the sound waves of the exhaust to help pull out the exhaust fumes and PUSH the intake mixture back into the cylinder! This increases the volumetric efficiency of the engine, causes the fuel/air mixture to be nearly perfect, and it's how the engine supercharges itself. So, when the engine is "on the pipe", it's getting more air and fuel. When an air leak is present, whether it be a bad crank seal or a bad gasket in the cylinder head, the mixture is leaned out considerably. This causes the engine to run like it does when it's 'on the pipe'. Because the engine is -dangerously- making more efficient power, it starts to rev. Well, more revs equals more air, which means more power, which eventually causes the engine to rev to the moon and seize due to lack of lubrication. There's nothing like the sound of a 500cc 2 stroke revving at 6k+ RPM seizing due to a lean condition... There's a LOT more to it than that, but it's the "2 Stroke Engines For Dummies" version. Koalification: I build and race vintage 2 stroke dirt bikes.

[@DirtRider500R]

Yup. You can also pulse tune the intake tract, but that's a whole other kind of crazy mathematics that I'm too lazy to get into. I find it rather interesting that you can COMPLETELY change the characteristics of the engine simply by changing the exhaust and nothing else.

[@pseudocoder78]

It's not either, it's just engineering. If you think it's magic, it's because you don't understand it. Edit: It's still cool and interesting either way. I'm just saying, "art" is what happens when you pour aesthetic acid all over it.

[@pseudocoder78]

Sorry, bad day yesterday.

[@davidthorne6796]

Correctamundo! OverRev!

[@Mark-nu5vg]

Years ago they did'nt have any type of radiator to help cool 2 stroke bikes so I imagine you've spent plenty of time replacing pisons and rings like I did my bikes used to run great until they really heated up then they'd lose power the newer dirt bikes are great now with the radiator cooling them.

[@nightwing6175]

Coming from a small engine mechanic, you did an incredible job explaining this.

[@draztiqmeshaz6226]

3:59 and obversely, you ain't getting any oil without things that grow. Long gamer here

[@georgschwiemann2353]

I have learnt a bucket load from you and am very happy to offer my resistance :) Re your question: Air leak (ie False Air) leans it out. Creates white or light grey plug electrodes (death white). In a high performance two smoke, infernal combustion engine, (over 10,000 rpms) excessive fuel is used to maintain the piston temperature below "jelly" state. In my 17,500 rpm race motor, we lean them out at the end of the straight to effect a pass (or prevent one). This is followed by choking the carby as we lift off to cool the piston and prevent a heat sink seizure. You can see the exhaust temp go up with the horsepower, 1100 to 1450 C. High silicon pistons turn to jelly around 570 C !

[@murkinstock]

I have the Poulan version of this, and it started getting hard to start and keep running, so I bought a special adjustment tool for the carb, and unscrewed both screws just a touch, and she runs like new again. They lean these things so far out to meet emissions crap, to where they suck, and will die quicker, because of lack of lubrication. Mines about 3 years old now, and still runs great.

[@Kevin-rc5ec]

This has to be one of the best explanations of a 2 stroke that I've seen. Thanks man!

[@vsetkoumiera7683]

The ABSOLUTE best explanation of a 2 banger engine on the lube tube !!! I’m not surprised though, since Mr.Ave is the teacher !!

[@treeguyable]

The air leak at the crank seal changes the crankcase pressure/vacuum dynamics, which are designed specifically for each engines running specs.

[@71dembonesTV]

"2 smoke infernal combustion carbonated engine" lmao

[@dhooter]

Here in Murica horse power is measured in bald eagles.

[@vincedibona4687]

"Celsius? We use Freedomheit!"

[@re-agent9364]

My car get 40 rods to the hogshead that the ways I likes it!

[@anthonydomanico8274]

Buck Shot, that made me laugh out loud!

[@asymptoticsingularity9281]

I am so damned proud to be a Murican!

[@UnacceptableViews]

@@asymptoticsingularity9281 lol really?

[@JaredKantar]

Here's a slick fun fact for the last few minutes of the video -- The reason you hone a cylinder the way you do is the small grooves left over trap the oil so you can get hydrodynamic (or hydroeleastic) lubrication of the piston/piston ring and cylinder wall interface. The small channels hold the oil. Ford is working on a new design for their cylinder liners where they laser etch small notches into the area near top dead center to act as litter reservoirs to hold even more oil. This is because as the piston slows down towards the top, its stribeck curve shifts and it goes into mixed and boundary lubrication. The larger reservoir of oil helps to increase the film thickness and thus off-set that stribeck curve shift -- lowering friction at that point in the stroke. Another use for oil -- Noise/vibration dampening. Some applications also purposely cause oil to foam a small amount to absorb sound.

[@waynegeordiesdad648]

I'm sure a thousand people have already noticed but first shot of the plug shows a crack...top to bottom Cheers from Canada North

[@panikrev175]

Staying up late pays off.. Jesus Murphy, bud, you're really choochin out the videos. Bless you, friend; you really make KZbin a great place to be at midnight.

[@The_R-n-I_Guy]

I've never understood how a 2 stroke worked. Maybe now I might take apart my old weed whacker. Probably not. But now I know what's going on inside. Thanks again AvE

[@minimec6183]

In the sixties, when I was a kid, I had this model engine, attached to a piece of wood. It was a 1 or 1.5 cc Frog. It had a compression screw and a very simple carburettor, hardly more than a needle valve and a nylon propeller. I spent hours trying to start the thing, the intention was to drive a plane with it in a circle attached to strings, once it was run in. It was a two-stroke diesel and it ran on a mixture of 1 part kerosene, 1 part ricine oil and 1 part ether! And no, there was no glow plug! It very seldom fired, occasionally it would wack you over the fingers.

[@flyingjeep911]

What my dad taught me growing up with 1:10th scale rc trucks.... Is that leaning the engine will give it more power. To my knowledge, it is gaining power from the increase in air. By achieving a more efficient burn, creates more power. You're not having the build up of excess fuel in the combustion chamber basically turning the engine into less of a "fuel pump".... But the downside of this is basically what's happening to your seadooooo... More air is getting in the system making the engine run more lean...a Less fuel mixture going through the engine means less cooling. Thus frying the engine or overheating. Then you shut the thing down and the head melts to piston. That's my theory, hope you see this and if I'm wrong let me know so I can learn too. Great vidjao :)

[@hiram4451]

A LEAN mixture always makes more power but because the temperature needed to ignite the mixture keeps dropping as it gets leaner it will eventually detonate before the piston gets to tdc and BAM!

[@k125bw3]

also one day that the thing wont chooch anymore because its pistone got holey

[@WeAreGRID]

Thats actually really informative, its not actually anything wrong, it just starts detonating before its supposed to.

[@18iser]

Or it will just melt right.

[@funkalicious2002]

Also, as the temperature of the burned mixture rises, the pressure of the gasses increases, which makes them push the piston down harder.

[@WeAreGRID]

Tyler Wilson right, so it runs better, burns hotter, goes faster, becomes easier to ignite, starts igniting sooner with more power and BAM throws the piston out the side because its too good at its own job.

[@SheepInACart]

Petrol motors, unlike diesel, almost always run rich. It helps cool and lubricate in exchange for some efficiency and a very small amount of power. However it also has a less obvious effect, in that hydrocarbon based fuel is an anti-detonant, so they can run more compression and\or more spark advance before it starts to knock or pre-detonate (which is compression ignition around still hot engine parts before the spark, or even pockets of compression ignition ahead of the flame front inside of the motor during ignition. In either case knock will wreck a motor really fast (like too fast even for drag racers to tolerate it), but just like intentionally running more spark advance it can result in slightly more power.

[@BlackBobby69]

Well, you learn something new every day. All this time I assumed it was a liquid...

[@MyLonewolf25]

Any knock will KILL power

[@mikeguitar9769]

Knock works great in a diesel, you just need a more skookum engine that won't be destroyed by that compression-ignition. And this would be too heavy for a whipper-snipper...

[@cleansedbyfire9223]

@AvE, I have come to use your skookum language since I first started watching your Vijayos. I’m finding your AvE-lish to be the most fun to work with. Thank you and God-speed for your country to improve.

[@garyn9704]

You're the greatest. Didn't have time to watch until I retired so I'm late and am sure your question was answered moons ago. I can't imagine me explaining something to you anyway but was the only op I would ever have. I was sitting at a Lawnboy Factory in 1965. You don't crank the carb screw until it runs pretty (lean). It needs to two cycle(rich) for lube and cooling. More air goes lean and burns it up.

[@nuggetzor]

i might need to send you money ave, I've learnt so much from your videos. i love them! keep it up i'm sure we all appreciate it

[@johnrtrucker]

2 stroke: turn me on baby! Me:starts motor 2 stroke: choke me daddy!! Me: what? 2 stroke: harder!

[@jonathandockstader1845]

Nice explanation of a two-smoke engine. As a two-smoke mechanic from a previous lifetime, I would like to add one thing about the carburetor. The other side of the carburetor, opposed from the fuel bowl side, is actually a diaphragm operated fuel pump. Impulse is channeled through a small port below the intake throat of the engine and is mated with a small hole on the carburetor. The impulse is generated from the engine crankcase's constant pressurizing and vacuuming caused by the piston moving up and down. This impulse causes the carburetor's fuel pump diaphragm to pulse while little flapper valves open and close within the fuel pump side. Thus fuel is drawn from the tank into the fuel pump side of the carburetor and passed into the fuel bowl side of the carburetor though ports in the carb body. Thought you might find that interesting. BTW, I love your videos. Fucking SKOOKUM.

[@AllongLawl]

13:14 "Very very fine conductors, lots and lots of them" Thanks for the analysis Donny

[@ChewbacaTW]

Why do your video's make more sense when I'm 3 sheets to the wind?

[@danielminskey]

it is true. :)

[@alfbittner6489]

Lot of things work better when you add alcohol.

[@FamilyManMoving]

@Alf Bittner: Not gas...Ethanol sucks.

[@spidergoose891]

People watch KZbin any other time?

[@MrSailstone]

ADHD

[@shltplease]

You are a great man doing dogs work. I showed my 10 year old this vagayo and now he knows how many strokes it takes to get the job done. Seriously though keep up the gud werk, I envy your eloquence and vast knowledge as well as your humility and humor. I wish you were among one of my awesome neighbors, we would have good times.

[@whatcanilearnhere9158]

didnt learn a thing from this that i didnt allready know for 40+ years, but really enjoyed watching. Ive had a few two strokes "scream off" from a crank air leak. i recall one time i had a 76 skee du against machines new in the late 80s. i noticed the chambers starting to glow and felt it rev up, so i just pinned the thumb to the par and let it loose, the finish line was in sight. i still dont know for sure, my best guess is the heat increases psi enough along with the lack of lube slowing everything down to win that race to everyones dismay. it kept running long enough for me to shut it down and crack a beer pretending that i built a better motor, but i knew it was still melting as i sat there

[@whatcanilearnhere9158]

rv 247 , no kidding, i found myself with my head near the front point of the machine to try to keep the track on snow, the skis where wanting to go past me and flip it all

[@snocrushr]

The reason a two smoke runs like a raped ape just before it gives up the ghost is because they can not run at the perfect stoichiometric ratio of fuel and air for maximum power and have the adequate amount of lubrication and cooling (provided by the fuel) at the same time. So when an air leak develops in the intake track more power is produced but the cooling and lubrication is inadequate and the engine seizes. Two strokes are designed to operate on the rich side of optimum air fuel ratio to allow them to live and this why they are considered "Dirty" engines.

[@jdrok5026]

But in reality a engine isnt dirty only the process of how the burn is achieved. You eliminate carbon and nitrogen methane etc and your left with hydrogen and oxygen your burn is clean but likely would require you to have a whole roost of things to keep possible rust from form. Is it possible yes is it cost effective no would green freaks admit its clean no because even water is bad for the environment now when its introduced as a vapor.

[@18iser]

I think the engine gets more rpm during the air leak because the engine is designed to run a bit rich to be on the safe side. So it could do with more air once its up to temperature I think that is the case for most engines. They are designed to run slightly rich because it is safer.... Or because it would still run good on different altitudes or whatever.

[@thomasschwarzinger7757]

if it is running with less oil in the fuel it is also going to produce more power....untill it is stuck or seazed

[@daki222000]

I think you are right, but the richer mixture is needed for cooling too. too lean = too hot, not enough cooling. An engine can run on a much leaner mixture if it is built to withstand the heat. moh powoh.

[@BradleyGrohs]

This is correct. when tuning a 2 cycle the low is tuned rich so when you punch it the engine dosen't lean out and die during acceleration. the high idle is set rich because when applying load to the engine that is where your maximum sustained power is. When it leans out the engine rpm will rises but loaded power will drop.

[@anotherhonda9402]

Haven't seen one of those for a while, I used to recondition those for the manufacturer Husqvarna (Electrolux) UK. Over here they were branded as Flymo or McCullough. Usual issue was fresh fuel required and the carbs needed tuning. Had to use a small Walbro splined carb tool. Think they were made in Arizona. They also made a line of hedge cutters with a design fault where the Woodruff key was cast in to the alloy flywheel. It used to shear off knocking the ignition timing out. Fix was a new flywheel with a steel Woodruff, but the keyway in the crankshaft was so small it caused the flywheel to fracture round the keyway and nocked the timing out.

[@stevemcilroy9518]

Another great video, cheers mate. 4 stroke, Suck , squeeze, bang, blow - Induction, compression, ignition, exhaust.

[@ptx_dk]

I just noticed that this exact engine is in season 28 episode 9 of "How it's made"!

[@GrantBrotze]

3am watching AvE whats new

[@stucknousernames]

have even sleep since a day and a half

[@Rockardo_]

rip

[@jimmymclemore9807]

+smcic I see what you did there! Big Clive reference!

[@bbsmyname]

I love watching AvE all night long. Invaluable information for me.

[@SummerFunMan]

"Am in the morning," SMCIC? So "in the morning in the morning," then. NICE!

[@vector3647]

This is like learning mechanics from Hunter S. Thompson...and it's fucking awesome. Keep up the good work Sir!

[@Jped277]

Hey Chris, I hope you're doing well. My name's Dave and I love your videos so much, I started watching them every day I've learned so much from you in the way of scientific terminology and whatnot. You got me curious, and I do know that you hate it when people suggest video ideas, but I think it would be awesome if you would do a video on tempering steel or metals. Possibly how to get a spring to be springy... And I would love to see your explanation of how to temper a blade such as my chisels or wood plane to hold an edge after sharpening. Please don't dog me too much for asking, but I love listening to your videos, and your the only you tuber who can keep my attention a full half hour for a video lol. Thanks again, keep up the good work, ur fan, Dave.

[@timothykelley4495]

Best and clearest explanation of the inner workings of a 2 stroke engine. SWEEEET

[@epicdreams1]

you know your stuff man, I learned alot about 2 smoke engines and then some. Great video man, keep up the good work!

[@blakewadington4390]

the reason a engine has more power when running lean is because engines are not designed to run at a perfect stoichiometric ratio. they are designed to run rich so the combustion chamber has more of a controlled burn than a explosion also running more rich will keep the engine cooler so you can have smaller clearances of things like piston ring gap and because you need to take into consideration heat expansion when you design an engine and when you have a hotter engine there is more of a risk of preignition which is the air/fuel igniting by heat and pressure essentially making it like a diesel engine. since diesel engines are fuel injected the you don't need to worry about preignition because the ignition is controlled by the time of fuel injection. that is one of the reasons you can't really have a reliable carbonated diesel, that and since diesel has a much higher viscosity than gas it would be very hard to atomise into a air/fuel mixture in a carburetor. thank you for your videos, you create some of the best learning experiences i could ask for, you keep us entertained while teaching incredibly interesting things.

[@ryanhodges7101]

Thanks "AvE" for making these "BOLTR" videos. I recently found your channel and I have really learned a lot and have been entertained at the same time. It's obvious that you put a lot of time and energy into making them. You have one of the best channels on KZbin. All the best to you and your family.

[@skelator_]

can you do this on a 4 stroke engine if you get the chance this was really interesting

[@TheBrokenLife]

There are some excellent animations on KZbin for how a 4 stroke works if you want to go check them out. A 4 stroke is actually a little easier to understand in animation since there are usually parts doing stuff inside the engine block that you can't really see while it's all assembled. Not like an old faithful 2 stroke that runs on bamboo and a couple of holes here or there.

[@USCisgay]

it would take 6 hours. hahahah

[@Q_Branch]

There are 4 stroke weed whacker engines, some run with a small sump, others run pre mix oil like a 2 stroke.

[@pseudocoder78]

4 stroke running premix? Explain how that works.

[@AttackratUK]

+pseudocoder78 Stihl have some good animations that explain what they call 4-mix, a 4 stroke running premix.

[@pseudocoder78]

Aesthetic Acid? That's a new one :D

[@timothyball3144]

At least it looks good.

[@redneckgunning8100]

you can tell ave is amazed to be explaning the engine. you can tell hes interested

[@jesselloyd207]

Skidoo uses isoflex permanent grease (on the popular 800r and others) to lube the crank bearings (not the oil). Hole in seal = loss of lube = blown crank bearing. So thats one reason they die. They also run lean with a hole in the seal. Lean = more HP at the expense of heat which can melt the exhaust side of the piston. Skidoo usually has a lean pilot and a more rich main jet: keep EGTs low at WOT but make ok fuel milage at 1/4 throttle, you can lean out the main for more power, but would risk melting the piston. Leak down test every summer for me, learnt from a plethora of past experiences. Thumbs up from the Okanagan!

[@droy333]

Every once in a while I wonder what you look like, then agree its better if I don't know.

[@wurkhardnomuny]

i just want to know what the man looks like

[@droy333]

Never know. He might take it to the next level one day. Doubt it though.

[@kasnitch]

judging from the size of his hands and forearms - I estimate he is 6' 2" and depending on if he is still in prime physical form as it appears he works in a resource industry - aka mining - maybe a svelte 203 pounds . maybe a 10 pound beer gut , since he is not front line , but possibly a millwright . just guessing . I've only been a sub for a couple months or so .

[@ORDLAND]

In an older videjo, that I don't remember the name of, his face was shown in a reflection. Highly regular dude if i remember correctly, with glasses, or maybe it was eye protection glasses.

[@devinerdmann5948]

as far as I can recall hes a mechanical engineer (I think he even has a phd as well)

[@stihltech206]

The reason that the engine raises in rpm is because it is governed by the fuel/air ratio. The optimum ratio for rpm is not the same as optimum for power. Most 2 strokes are designed to run a ratio geared towards power output and therefore when a healthy 2 stroke is held at full throttle it will start "hunting", or fluttering between rich and lean, trying to find the safe medium. This is not to be confused with the built-in rpm limiter that can be found in some higher-end brands that will flutter the spark output at high rpms. Soooooooo, when an air leak occurs at one of the crank seals (usually clutch side) it will find a ratio which better suits higher rpms until it eventually gives out due to the added friction of rotating faster than it was designed for and lack of lubrication due to fresh air being sucked through the crank bearings instead of oily mix.

[@rasalas2x]

An interesting 2 stroke was designed and built as a "Martin" outboard motor. George Martin was a hydroplane racer who designed and built poppit valve 2 stroke racing outboards as a subsidiary of the National Pressure Cooker company. Totally cast aluminum for light weight and lobe operated intake valves which are far superior to flappy reed valves which require back pressure to seal. In the early '50s his rising dominance in the racing world raised the ire of Carl Kiekhaefer (Mercury Outboards) who then threw a couple million dollars into his R&D and not being able to compete at that cost National Pressure Cooker defunded the outboard division and hence the demise of Martin Outboards except some steadfast restorers and collectors. A few other great features include screw adjustable tilt and full 360 deg steering eliminating the need for reverse gearing. Wonderful and beautiful product design. Check them out. My little "Martin 75" runs great and is a joy to operate.

[@wpowerwagon]

Taking things apart, this is how you learn how things work and it makes you a better mechanic, this is how my dad taught me how and why things break down, and that little trick that this little two cycle engine does when it speeds up is a weird mistery, yeppers it'll make you shake your head

[@alandaters8547]

The clue is at the very beginning- this is a "weed eater"" and can be replaced by other weed eaters, such as a goat. No mining or drilling necessary and low maintenance too.

[@JefK]

And they're edible

[@outcast9486]

YAY!!! I learned something!! Always fight with the carbs.

[@someoftheyouse]

Excellent description of the operation of an 2 stroke. Right down to the nuances, fucking bravo. As for the lean burn question there's a few factors. The main one is with a higher air to fuel ratio (AFR) complete combustion is achieved and VERY quickly. This leads to a very high peak combustion temperature as well as some decomposition of nitrogen etc although I don't know if NOx is a net positive or net negative heat wise. It's this high peak combustion temperature that wrecks pistons etc. It also causes other engine wrecking problems like pre-ignition. The extra power comes from the complete fuel burn and additionally, an engine with a fixed ignition timing will be a compromise between a low ignition advance that will idle well, and a larger ignition advance that will make power at a wider throttle setting. As the AFR goes up the combustion time goes down, meaning that the ignition timing gets closer to ideal. The engine makes more power that it was initially designed too. You also have less fuel charge cooling. So in summary you have a very high peak combustion temperature producing more power and suddenly your engine is widely out of design condition and your two stroke goes all blue smoke. #letdown.

[@jonponton]

I've watched the majority of your vi-jayos. Doesn't matter what the subject, you always explain things in a really easy to digest way. You're a friggin champ!!

[@nathanharland3375]

From what I have noticed from racing 2 smoke sleds that when you run it lean, due to crankcase seal on clutch side or removing air box, that it would rapidly heat up the piston causing super high compression. Like you said it runs like a raped ape but the cost comes at putting new rings and piston in it every season.

[@nathanharland3375]

And also something to wrap your head around that on skidoos in order to get the sled into reverse they stop the engine from clockwise to counterclockwise without using a starter and without fuel injection.

[@tayro7265]

My thoughts on the "Raped Ape Effect" or RAE had to do with fuel vaporization. When it runs out of fuel it first runs out of liquid, plus or minus a surface film of liquid fuel. This film is under a vacuum, vaporizes at just the right rate as to have the perfect flow of pure fuel vapour to air ratio. Liquid gas burns, be it quickly, vapour explodes, right?

[@SummerFunMan]

Or any brand of 2-stroke-powered snowmobile/sled, Nathan; not just Ski-Doo.

[@alexmcdonald207]

Oh man, now I know what it's like to be an elechicken watching an electronics video of yours.

[@matthewkriebel7342]

It's the target audience, and a really good part of the channel. People go from being curious but knowing nothing, to knowing enough to be dangerous. But most people don't stay there. They move on. AvE pushes people into that dangerous but fun region.

[@GunFunZS]

close. He's an intersection of above average understanding Venn diagrams for a bunch of feilds of technical knowledge. I think most of the audience knows a thing or three about a few feilds, and he knows just a few more. So he gets us up to the danger zone in coupla more things. I know a smidge about machining, ditto about welding, a bit more about engines and hydraulics (sans the math), enough to not like the pixies, a bit about leather and dead trees. I come here and see him do projects I've contemplated and show the tricky parts and the easy and give rule of thumb calculations to get close enough to work.

[@thaweezl8852]

Thank you for trying to explain this to me. Regretfully my gray matter is not acting receptively to logic. I was following along perfectly... and then the video started. It’s almost like another language. You clearly know what’s in your hands. I have the technical skills to tell that it seems to be made out of metal.

[@tylerpripps4969]

+AvE I have the exact same whipper. I thought the carb was non-adjustable too but it just requires the right tool. I found the tool was $15 so I just took a needlenose pliers and turned the screws all the way out. Then I took a spinning hack saw (Dremel: don't judge) and cut some slots for using a screwdriver. Now I can, and have to, adjust them every time I use the blasted thing.

[@josippenezic7106]

I'm sorry that I do not read all of your comments. Maybe someone explain why works better with pierced oil seals. 1. It happens because two-stroke engines need excess fuel than four-stroke engines and you have an extra air while actually works much more effective just do not have enough lubrication (for that the is damaged piston). 2. Probably the engine control maximum revolutions over the carburettor but if you have additional air (from pierced seals) you have an additional exhaust that creates an additional vacuum in cylinder for which you get more mixtures of carburettor and more air (from pierced seals) until the cycle arrives to the limit. 3. In order to achieve higher power and RPM you need to have just a certain amount of air, which you have 4.When you see that this is happening stop the engine because you could get a the piston in the back of the head;). I've never seen such a sorry crankshaft with open one side and for .God's sake do not buy such trash.

[@LucidAutowerks]

"Noozle on the hooze" is my favorite Simpson's quote ever!

[@fxvg7091]

Thanks for being thorough. It's rare to watch a video of yours that I understand, but I'll get there. Keep em coming!

[@dean-543]

I haven't read all the comments yet, but the Hi/Low adjusters are probably "DD" screws. I have this on my ryobi weed eater. Take a grinder or a hacksaw to make a flat (standard) screw head. Got that tip from Steve's small engine saloon.

[@TheRanblingjohnny]

Here's to you, Choke-and-Stroke!

[@nickk3226]

I do recall a lot of loose doorknobs...

[@duhbaws2705]

I fkin love the way you talk. I also learnt me sumtin.

[@iknowyourebrokeauto468]

I love it when he talks about things coochin. lol

[@idahomike]

Excellent video. I was already pretty comfortable with 2 strokes, but the way you explained it was fantastic. Very thorough, while still being easy to follow and understand.

[@matthewcarwile9235]

Hey AVE, I am probably wrong but my understanding is that you start rich and change the air:fuel ratio to make it more lean once you're going. The additional air is to allow the fuel to burn more full and longer giving you a better stroke. Thank you for another great video.

[@TwilightTheShooter]

"That is when the two stroke engine is supercharging it's self" so you're saying that they start to blow themselves at a certain point? I'll just show myself the door, thx

[@godfreypoon5148]

I heard they had to remove a rib or two to let them do that. I guess that would make them run hotter?

[@jkd2377]

Google(two stroke exhaust design) tl;dr Resonances. High/low pressure waves from converging/diverging sections of a tuned exhaust can both help suck fuel/air into the cylinder and push back some of the excess good fuel/air that the self-suck produces.. The frequencies and the resonance bandwidths are adjusted to build a sweet range of rpm's. Yay 2-stokes!

[@SECONDQUEST]

+JKD the jokes

[@kainhall]

when when the engine hits its Vtec. intake post is closed, exhaust open.....exhaust pressure wave reflects off of the tuned exhaust, forcing a bit of fuel/air that came out of the exhaust, back in..... when not in "vtec" this isnt getting all the leaked gas, and isnt raising pressure in the combustion chamber before spark. when "vtec kicks in yo" (the power band) its getting all or most of the fuel air, AND raising the pressure pre combustion. just like a trubo on a 4 stroke does. but with out the weight of said trubo, or lag. 2 stokes are fucking genius!

[@Gmaniacable]

it just goes like skunk untill the piston gets too hot and or melts a hole in the head, of seizes because it "grows" bigger then the bore

[@ufohunter3688]

On a Cessna 152 or 172, you get to fine tune the richness for cruising (save fuel). You adjust to lean it slowly, until the head temp starts to climb, then you back off 3 turns. If you go too lean, you kiss your engine and your ass goodbye. !! You use fuel to cool the engine and also to prevent ice build up in the carb. That's why, on take off and landings, you go full rich.

[@MorganOliff]

great video. thanks for the link to donyboy73's channel too. hey I believe the switch grounds the magneto, instead of interrupting it.

[@Peter_B_]

Great video! What a great engine design. So few components. The way the spark is made is pure genius. Simplicity cuts cost and gives power to the people.

[@TonyFleetwood]

R.I.P whipper snipper :( 2009-2016

[@TonyFleetwood]

also oil = hydrodynamic suspension.

[@joshpicard4139]

its all shits n giggles till someone giggles n shits

[@chrisgrey9204]

The one thing I'm surprised you didn't cover is how these tiny 2-stroke carbs require the crankcase pressure pulsation to work. Traditional carbs use the venturi effect alone to coerce the fuel from the bowl, through the jet(s) and into the air stream. However these tiny 2-stroke carbs, for being so simple, are actually a tad more complicated than that. They require the pulsing of the crankcase pressure to "work" that diaphragm which both acts as the fuel pump pulling fuel from the tank (which may be physically below the carb) and literally pushing the fuel into the intake air stream. Notice on the mating side of the carb that bolts to the engine, there are 2 tiny holes along with the big hole in the middle where the intake air/fuel mix enters the engine. One (or both) of those tiny holes connects the carb to the crank case. Unlike the main air/fuel intake, those holes expose the carb to the crank case during both periods of vacuum and pressure. Some might be thinking, vacuum and pressure? Yes. Unlike most 4-stroke engines where a pressurized crank case is generally bad and thus why you need a vent or PCV valve to relieve it, a 2-stroke's crank case is under both pressure and vacuum by design depending on where the piston is in it's stroke. When the piston is near TDC, the crank case is under vacuum. The vacuum is what aspirates the air-fuel from the carb into the crank case. But at some point during the down-stroke, the vacuum turns to pressure. It's somewhere near this mid-point in the stroke that the piston blocks off the entry way between the crank case and the carb. The pressure would continue to rise as the piston approached BDC, however just as the piston blocked off the crank case from the carb, it opens an entry from the crank case into the combustion chamber allowing the positively pressured crank case to push a charge of air-fuel mix into the combustion chamber while at the same time evacuating the previous stroke's exhaust from the chamber. It's not surprising that a fair amount of unburned air/fuel mix gets blown out with the exhaust which explains all that oil you pointed out on the muffler. You can think of the location of the carb and combustion chamber ports in the cylinder wall as analogous to a 4-stroke engine's cam shaft. Their size and location contribute to the engine's powerband.

[@ShawnDickens]

Great start out video for people learning. So many claim to explain and leave out a ton of needed details. Could be more organized, but the info is there and this way more important. Good job.

[@thegardenofeatin5965]

I used to play bass in Aesthetic Acid.

[@bryankirk3567]

Really good band. Great use of feed-back!

[@parillo12]

even though I know my 2 smokes... I still enjoyed a recap

[@robs7180]

The air leak on the crank seal allows the engine to suck in more air - increasing the ratio of air to fuel, ( in effect, acting like a secondary carb butterfly that has been opened slightly ) so by getting more air the engine responds as if youv opened the throttle and so it speeds up. Someone has probably answered the question already but what the hell Thanks for the detailed video fella ! Keep yer pin out the rice !

[@brysonshomaker7094]

Hey I’m a 17 year old hoping to be a mechanical engineer and enjoy your videos and wanted to say The stoichiometric ratio for gas not including oil is 14.7 to 1 that is where gas burns with the air cleanly and completely and makes no harmful gasses but engines do not make much power on this ratio so they have to either richen the mixture or lean it out and it’s battle between power and getting preignition the leaner the more powerful but the more susceptible to preignition also why running higher octane fuel can go leaner on the same compression ratio and not knock compared to lower octane fuels which is why the two stroke runs away if there is a leak it’s more air more lean more power so she gets to choochin way faster and blows herself up

[@user-neo71665]

The idiot at the EPA that thought potting the carb adustments and making them need a special keyed screwdriver a good idea needs to be given one of these that the carb is so bad out of tune out of the box and be required to mow my 80 damn acres with it.

[@hsbrooks]

I thought the needle locks originated in California. Doesn’t matter. The first thing I do on purchase of a new 2-cycle engine is pull the needles and strip off the plastic limiters

[@clydeperrine2959]

@@hsbrooks Or just take your Dremel and carve slots in the heads of the jets. Yes, it will also carve slots in the protective housing around the jet heads, but so what? Now you can dial in the idle and high speed according to your area of the world. There are KZbin video's showing this process. Bob's your uncle.

[@Photostudioww]

Take a cheap pen apart and use the tip as a tool to adjust the carb. If yall don't want to buy a dremmel.

[@trondwell13]

@@clydeperrine2959 did that 40 years ago before youtube

[@Sizukun1]

Any idea why there aren't more 2 stroke diesel engines for small applications such as weed eaters and lawnmowers? I would assume they could be built more simply and wouldn't need a magneto and more parts to fail. You might need a glow plug warmer like RC cars, but it potentially would last forever right?

[@fordrac1ng81]

Diesels are heavy, and have to be built with forged parts and 2 stroke diesels don't run without forced induction. (look at old detroit engines that had both a supercharger and a turbocharger) For many reasons, 2 stroke gas still reign supreme and will until outlawed.

[@dude998866]

Not to mention that all two stroke diesels need blowers to idle. Again, too many $$$$

[@coollasice4175]

Why would it last forever?

[@Xr4di4ti0nX]

+AvE Exactly! to do it right you'd want direct injection which requires a pump, regulator, and injector plus all the componentry to control it all. this is WAY more money than a simple to stroke with a carb. some dudes will say two stroke direct injection is the future of consumer internal combustion engines.

[@Xr4di4ti0nX]

+Nick Brueggeman simple TWO stroke****

[@jeromewink557]

Paid $75 for one of these many years ago. Worked great once. Next use couldn’t keep it running. All carb screws blocked off so no tuning. Went straight to little engine heaven.

[@barrylast8655]

Love yore Commentary & Advice! Reminds me of my uncles. Regular delight and even the disagreements (arguments). Real life, as we get things done, Right! 👍😁

[@PeterOekvist]

This is how you talk after a stroke.

[@PeterOekvist]

Imagine your brain after a 2-stroke...

[@honda2363]

Where can I find one of those fancy scopes? Dog knows that would have come in handy after my timing belt went. The engine survived incase anyone cares.

[@71dembonesTV]

That's great news a timing belt breaking on a is usually a death sentence. I want one of those things too

[@tinylockpicksinc.1758]

Your engine surviving a broken timing belt probably had something to do with that is most likely not an interference motor

[@godinnlives1591]

+ AvE The reason the engine seems to run so much better when the mixture is leaned out is due to the optimum mixture of air, furl and oil. It is able to burn ALL of the mixture (damn near) and as such it sounds and runs fantastic. However , when it is at that optimum state there is NOT enough oil to keep the pieces lubricated and it actually burns a lot hotter since it is ALL burning and there is nothing left to help carry away heat. Hope that helps.

[@jfr55man]

one thing to note, in addition to adjusting the fuel/air ratio the choke increases the vacuum beneath it, helping to atomize liquid fuel while the engine is cold.

[@louis5668]

My girlfriend says I have a 2 stroke engine...

[@lebeshahmed5358]

Suffering from preignition ?

[@louis5668]

@@lebeshahmed5358 😂😂😂