Yamaha 2 Stroke Engine Theory And Diagnostics

This is a copy of a VHS tape Yamaha 2 Stroke Engine Theory And Diagnostics.

[@fredwilliamsonmiller7214]

As I struggled with a non functioning small 2 stroke engine on my leaf blower ( suddenly after 3 or 4 years of good service), and trying everything I could think of, I stumbled into a video about a unit with many of the same history/repair points as my unit. That engine was repaired by tightening of loose bolts, cylinder to block, which was permitting air leaks. I checked my engine - rock solid but while there I chanced to remove the blind end plastic crankcase cover. Nasty hole in this cover so I went looking for detailed info on what could this mean to the engine function. This video was just excellent......no vacuum on the upstroke (no fuel and air into the crankcase), no pressure in the crankcase on downstroke to move the mixture into the combustion chamber and lots of air leakage. Repaired the hole......my leaf blower is just fine again. Thank you

[@matthewfredrickmfkrz1934]

I wish these guys could link da toos for advertising n sheeeit

[@jdsstegman]

Now you are certified yamaha technician!! You could be hired at any dealer tomorrow!! Weight and power is always a concern of mine!!

[@coolhandluke1503]

If weight and power is such a concern, then put down the burger and get back to the grind?😂

[@EarthSurferUSA]

If one vid offers that much qualification, "I am a pro after one vid!", I can see how our education system failed you. You should sue. Not being offensive to you. I just can't stand to see the mental sabotage to our society. The result is, we are not really good at anything anymore, even if we think we know what we are doing. But you can demand double the pay, because it is twice as hard to figure things out. lol

[@vijayam1]

Brilliant. Please share more videos like this, these make a TON of difference to one's ignorance..

[@EarthSurferUSA]

From the Yamaha engineering. That is why it is pretty darn precise and inclusive with the factors involved. Not a YT yahoo, or a brain dead AI bot channel vid.

[@axkoula7851]

I believe that 2 strokes are closer to musical instruments than machines. To me the sound of a crisply jetted one ripping through the gears is music.

[@eniggma9353]

This video so old that in my headphones one side plays music the others the guy talking. Only realized half way through 😂

[@DavidSmith-tu1nd]

Yeah I only left my right ear bud in. No music. Perfect. Lol

[@vigorousboredom7016]

I had to adjust the audio balance so I didn't have to listen to that annoying music from the 80's or 90's. I prefer videos like this with no music.

[@EarthSurferUSA]

I think you will find often, that older vids from competent people (like this one from Yamaha engineering), and not people with their own agenda's, (environmentalists for example), will have the most solid information and based in reality. I build/modify 2-stroke engines for a living, (and learned a couple things here), and this is the best vid I have ever seen. Don't ignore the old guys with experience, even if the teachers today tell you to,---or you will be starting from scratch with the real learning curve. The vid is not that old. You are young and it just seems that way to you. I was there too. :) Doug in Michigan

[@richardchileshe9910]

Hi. I bought a brand new CF MOTO 450RS motorcycle and from new, gear changes were rough and it had vibrations. After the first service, the bike felt a lot worse, and engine was over heating sporadically. At 1400klm I realised when the dealer said that it was normal and I had taken the bike back 6 times, back to the dealer, I investigated the problem and found the dealer was filling the oil to below the empty level. When I toped up the oil, it took 750ml to get it to the full line. That's 1/3rd oil missing since new. In the cf moto user manual it states that the oil should only be filled to below the low line, but in doesn't say if this when the bike is on the side stand or upright on a service stand. Turns out they were filling it up on the service stand in the upright, and those instructions were for the bike being on the side stand. So dealer was filling my bike and some others short of oil. Engine now sounds rough compared to new bike and I am hearing a slight ratting sound. Can you please tell me, during this crucial run in period, what is the potential damage to the engine and gear box? I think during the crucial 1000klm run in period not having enough oil to meet even the bottom line of the low indicator mark would have caused damage, but dealer said no, it's o.k..

[@EarthSurferUSA]

How can you "fill below empty"? Not many real good mechanics around today. IMO, you are better off learning it for yourself. Today,---education starts after graduation, but you have to make it happen yourself.

[@grubby1975]

Thats not right. If you use the side stand to check the oil, it will be lower than what it says when in the upright riding position. You are overfilling the crankcase which is causing windage, (the crankshaft and lower ends of the rods are being submerged in the sump oil and slinging it throughout the crankcase which is adding considerable weight to the rotating assembly which will make it run rough, possibly smoke and could knock a bearing out as the oil gets whipped to a froth and doesnt separate fast enough before it goes through the pump/journals and bearings). Hope you understand my explanation, Im a mechanic, not a scholar. 😅

[@NiiJiiLuv]

These Queen got them moves on point ..I love it!!.

[@MrJeffharper47]

Cool video. Watched the whole thing as I’m about to buy a YZ250!

[@RetroVideoArchive]

Good choice!

[@donniebaker5984]

this is the first video closest to the truth of the reason a 4 stroke will never make as much horsepower as a 2 stroke of the same displacement ! now watch the video again and again and listen as its told pressure is forced higher than the incoming air trapped by the reed valve as the piston is making the compression in the crank case 1st that is much higher than the air than enters the carburetor ...we call this condition supercharging by no other name .and when he stress the fact that it is a sound wave that blocks the supercharged air from escaping the exhaust port as the piston now traps the supercharged intake air/fuel and compresses this mixture the 2nd time into the combustion chamber right before the spare plug explode the mixture with no telling how much more force than a 4 stroke of the same displacement but i will say that Yamaha knows along with KTM , Husqvarna and GasGas who has their MC 125 two stroke making 40 horsepower that is roughly 20 horsepower that Honda's pro CRF150 R motocross racer that on a good day barely makes a claimed 23 horsepower while the GasGas is in the 1st turn while the Honda is still clearing the gate after a little cuttie turns the 5 sec board sideways skipping off the track wearing a skirt and top she out grew years ago

[@waynegarfield6607]

Once upon a time that may have been true about 2 strokes having more power than a 4 stroke of the same displacement but not anymore. A yamaha 250 f can make more hp than a yz 250 . The reason is the,compression ratio. Follow the 2 cycle on a complete cycle again and observe that as the piston rises it doesnt start true,compression until the piston completeley closes,all the intake , transfer and exhaust ports which is about halfway of the upward intake , exhaust then compression stroke, AND,the power stroke,has the same situation , it only has a,2/3 or so true,power stroke before a giant hole opens up and bleeds off any expanding gases that could act upon the piston face if it didnt. Altho the 2 stroke has primary compression in the crankcase area under the piston and has a power stroke every time at TDC or twice as many as a four stroke it doesnt have the efficiency of a four stroke in the Carnot cycle or PVT ( pressure - volume - temp relationship which has a total duration ( some can have more than 180 degrees,of compression or power but to some extant ot is 180 on each . A higher compression ratio is a more efficient engine and doesnt waste the fuel as much and also has a better lubrication system than the total loss of burning it . However where the 2 stroke shines over the 4 stroke is power to weight. Very light, simple and cost effecrive do to simplicity and less parts to machine.

[@donniebaker5984]

@@waynegarfield6607 why are you here ? your total ignorance of engines is pathetic ..i am an apprentice of the late Hideo "Pops Yoshimura the most famous tuner of all times knowig more than you anyone else ..as now i have all his knowledge and YOU DONT

[@donniebaker5984]

@@waynegarfield6607 what you said is impossible simply because 4 stroke dirt bikes are not supercharged but 2 stroke dirt bikes are internally supercharged by the double action of their pistons that was said to be true by Hideo "Pops" Yoshimura , the man who invented honda's very 1st 2 stroke called the Elsinore ..ever heard of one ? they are the bikes that make that Braaaaping sound when your being passed and yelled at "get outa myway bitch"

[@Nudnik1]

They skipped overheating and air leaks from worn crank seals . I went to Yamaha marine school then . Excellent 👍

[@RetroVideoArchive]

Thanks for sharing

[@vigorousboredom7016]

I had a 1983 Yamaha YZ125 dirt bike that had worn crank seals. One day, the engine RPM suddenly increased to a very high level un-commanded and I had to press down on the kill switch for several seconds before it finally died out. After that, it never started again until I sold it to somebody who went through the whole engine with a fine tooth comb and replacing all worn parts.

[@Nudnik1]

@@vigorousboredom7016 yes..Lean out can cause piston seizures crank rod bearing fail from no oil and not lean mixture.

[@EarthSurferUSA]

It talked about lean conditions from air leaks, and even showed a "leak down tester" to find them. So----how did you do in school? :)

[@EarthSurferUSA]

@@Nudnik1 Yea,---I would not let you work on my stuff. Did you just make up a phrase, "lean out"? I don't even know what that means,---so say "a lean fuel/oil mixture", (not enough oil or none in the gas), and differentiate it from a lean fuel/air ratio. Both can cause piston seizures.

[@waltercleaton3470]

Excellent video

[@RetroVideoArchive]

Glad you liked it

[@koperaljali3253]

old videos are always the best

[@EarthSurferUSA]

Not always. But this is from Yamaha engineering, and engineering is the study of reality, (sans environmental engineering).

[@mehmetpoyraz3306]

Aslında iki zamanlı motora temiz hava enjeksiyonu ve yakıt enjeksiyonu olmak üzere iki enjeksiyon ilave edilse pistonun üst noktasından uygun bir yerden önce hava sonra yakıt enjekte olsa dolayısıyla piston yakıt girişi iptal olsa 4 zamanlı motorlardan çok daha avantajlı olur.yani motorda yakıt girişini iptal edip yerine pistonun üst noktasına iki minik mesela 2 milimetre çapında giriş biri hava enjeksiyon ötekide yakıt enjeksiyon olması çok daha iyi bir yanma sağlar.piston yukarı çıkarken henüz egzoz girişi kapanmadan önce temiz hava, egzoz girişi kapanınca ardından yakıt enjekte olursa mükemmel bir yanma olur.Tabi bunlar aynı anda görev yapmalı ve ikisininde geri tepme ventilleri olmalı . Bunlar hava ve yakıtı çok basınçlı bir şekilde püskürtmeli.Bilmem anlatabildimmi.

[@rudydalessandro1094]

Very nice.

[@lamina666]

People are so smart man

[@njmxjunkie3128]

Which 2 stroke engine is that they are demonstrating? What was it used in and what was the displacement

[@blueyhis.zarsoff1147]

Jet ski engine

[@njmxjunkie3128]

@@blueyhis.zarsoff1147 cc?

[@honingholes7026]

After watching this it explains whe I'm having trouble with my Morini Franco 50cc, I had low compression and bought a cheap Chinese replacement piston which is slightly higher at the crown and now I think that I should have paid more and got an original one.

[@danielfrazier840]

It'll be fine back the timing of some if it starts pinging

[@honingholes7026]

@@danielfrazier840 Thanks for the replay, but I defo should have bought a suitable piston, I've damaged the Nikasil plating on the cylinder and it will cost me plenty to put right.

[@RCTUN748]

你可以將汽缸頭進行平面修整，可以『技術性』的修平大概0.1～0.5mm不等的厚度，這樣你會有很好的壓縮比，當然，精細的計算過會更好，而且有一個備用的汽缸頭永遠是最安全的事情以免造成不可逆的後果。不過聽你的描述，假如汽缸沒有磨損，說不定你只要更換活塞環就能恢復很好的汽缸壓力了。

[@EarthSurferUSA]

@@honingholes7026 It is hard to damage a good real Nikasil plating,--and there is no shortage of crummy plating out there today. I doubt you had the good stuff.

[@RustyInventions-wz6ir]

Just found your channel and Subscribed. Very nice video. Thanks

[@RetroVideoArchive]

Awesome, thank you!

[@j.m.5995]

While a 2 stroke might have a power stroke every revolution it is hardly able to extract the full potential of the cylinder pressure built up during combustion before the exhaust ports are opened and the cylinder blows down

[@arsenictv7538]

Can’t learn anything with that music

[@RetroVideoArchive]

Listen to it in stereo the music is mainly on the left channel the dialog is in the right channel.

[@MykeHawke-r9r]

Thank you

[@hamalatsubuh4867]

Why do not put exhaust port lower than intake port?

[@NoelBergqvist]

... you are not smart...😂

[@RCTUN748]

我想你可能並未真正明白整個過程，對吧? 簡而言之，如果排氣口低於進氣口，那麼壓縮行程時，可燃燃料怎麼辦? 將與大量的廢棄待在燃燒室了，想一想吧～

[@trxtech3010]

2 Strokes are such garbage