BASIC THEORY AND OPERATION OF THE STIHL 4MIX HYBRID ENGINE

[@EngineKrahnicles]

Accidentally bought a 4 mix eater. When I read the manual, it says it's a 4 stroke and that I still need 50:1 fuel. Got really confused, so this video is very informative. Thanks a bunch

[@billloomis3907]

Don't want to say I'm old, but never heard of such an animal - Thanks for the info

[@johnschultz9947]

Lawn Boy school was in 1974, things have really changed in the two stroke/four stroke world. Thanks a lot.

[@jeremyrobinson4064]

EXCELLENT VIDEO YOU EXPLAIN THE WORKING OF STIHLS ENGINE SIMPLY SO THAT ANYONE CAN UNDERSTAND ITS LUBRICATIONS WORKINGS . IVE GOT THE BR800 & WAS SHOCKED WHEN DOING MAINTENANCE THAT IT WAS A FOUR-STROKE DUE TO ITS TWO-STROKE OIL MIX . THANK YOU FOR THIS INFORMATION

[@KensSmallEngineRepair]

What don’t they get? There is no oiling system(flinger/pump/sump) so the oil/gas mixture lubes everything like a 2 stroke, simple. Great video Jeremy!

[@josephherron7671]

Remember, they're not all razor sharp individuals. They only understand things that are explained in detail to them a dozen or so times. Throw something unique at them and they just can't wrap their heads around it.

[@freedommowers420]

Thank you for the explanation on the 4mix. I’ve never dealt with them yet but now I know. Greatly appreciate you breaking things down. 🤘

[@Terry_Baker]

Been learning about these engines in my prerequisites for my Stihl Sliver classes . Great little engines

[@THEMOWERMEDIC1]

Awesome. I took the bronze and silver but never went to va beach to get my gold

[@ltrbuhq]

I don't want to jinx myself but I love my fs 91r, 111, 131kombi, br400 and the magnum backpack blower. They have all paid for themselves many times over. I had a fs111 that just never ran right outta the "box", I wasted time at night after a long day of mowing trying to fix it [ new carb, valve adjust, tune up kit], I got frustrated, grabbed it by the trimmer end, swung it like a baseball bat and smashed it against a tree and I am still not sorry. Learned my lesson, time is money, I just go buy a new one if it aint anything a simple tune up can't fix cause they make me enough money to do that with them, Thanks Stihl, well done!

[@timberray9572]

I bought my first trimmer with a 4mix engine three years ago, I basically use it as a brush cutter and it gets used hard and its holding up well.

[@6900pilot]

Thank you for explaining that, I could listen and learn from you all day.. I have that exact model myself and I allways wondered how the 4 mix engine worked. Have a nice day.

[@alexcarr8503]

Thank you for the explanation. I own one of these engines. I really like my Sthil trimmer. The issue I have is, when it is cold or cool it will not Rev up. Hitting the throttle causes it to bog out. When it is time to trim my grass I start the trimmer and let it idle for ten minutes. Then it works fine. OR, If I trim with it bogging after 10 min it clears up and works perfect. Air filter is clean. Spark arrestor is clean. No proplem with the tank vent. Seems to be temperature related. ????

[@michaelchance9405]

Great video on the 4Mix, Jeremy!

[@robertmailhos8159]

Great tip of how a 2 cycle four stroke engine works next video you show the difference between the two styles of those small engine s 👍

[@adnacraigo6590]

I appreciate your explanation and tutorial. Thanks.

[@josedejesus6185]

Thank you, thank you very much Jeremy! Your videos are always full of surprises and great information! Keep the coming! 👏👏👏👏

[@northminer]

Like the way you explain things . Could you give the stuff you plan to work on a quick cleaning with air so it shows all parts clearer. I find it also lessen the dirt intrusion and makes me feel like I am working on something worthwhile. Keep up the good work , thanks.

[@THEMOWERMEDIC1]

Always do

[@matthewbeaver5026]

Is there a way to get a good look at the piston? I took the muffler off but that doesn't do any good with this design. I'm afraid my 131 was leaned out to far. I've corrected it by swapping to a carb that hasn't been adjusted. I'm just curious to know if there is any damage from the 3-4 hrs of use with the carb leaned out. Can I see it without breaking it all the way apart?

[@bobhanke6401]

MM1, It would be nice to have the part number for the upgraded cam gear cover on the Stihl 4 mix engines. In the video, there is a blob of trash on the last 4 numbers. Some suppliers are still pushing the old covers from their stock.

[@joeortiz3455]

What mix ratio would you use Mr j, I mix somewhere around 40-50:1 with my machine

[@robm.6825]

4 cycle nitro rc airplane engines have used a 2 cycle mix since at least the 80s. I wonder if it is where Stihl got the idea.

[@TheRustyRooster]

Great step by step explanation well done, this will help everyone out

[@jdclay1547]

@THEMOWERMEDIC1, I know I'm late to the video was working on a bunch of these, but what in your opinion makes these better than a standard 2 stroke, power torque ECT. Just asking.

[@THEMOWERMEDIC1]

Way WAY MORE torque at lower rpm

[@jdclay1547]

@@THEMOWERMEDIC1 Thank ya, I seen your video where you showed the updated cam cover is that for all 4 mix FS90-131 what's the part number? If they'd fix the cam pin issue and a better designed air filter seal I'm seeing dirt sucked past the filter I'd probably come around on my opinion, I work for a local park maintenance company in Huntington WV and the guys just wear em out, what bothers me is the place won't send to a machine shop to fix the cam bore, they'll run em till they die. So kinda of half like half hate relationship far as I'm concerned, the torque is nice but for high rpm 8hr a day in n out I'm having trouble seeing how anywhere else they'd hold up. Pole Saw or edger is about all there good for in a setting like ours. I'm absolutely filthy when coming home from a day working on one 4mix to lol

[@jimmydickson8854]

Thank you now I know how it all works air leaks priority for good running ,old jimmy Aust

[@RaleysSmallEngines]

Great detail MM1. Yep some people will argue with a tree stump LOL.

[@BigT962]

Good to know! Awesome explanation. One question, what is the advantage of this design vs a regular 2 stroke?

[@banjoford1214]

Emissions?

[@haydenshores9943]

Yeah it's less emissions and also less noise better fuel milage

[@lamarprice5680]

Grease looks good on you 😝. Great video 👍

[@patagualianmostly7437]

I'd earlier watched another of your vids (where you changed the crankcase seals.)....and I thought why does he keep saying "4 mix engine" ??? I could clearly see it was a four-stroke.....I, like others it seems, was somewhat puzzled! As they say..now: "Alles Klar"...... I've yet to come across one in this neck of the woods..(South America)..but now I am well armed with the right info....Many thanks! Big Thumbs Up.

[@Jamwcjconn]

Excellent video 👍

[@themaniacmower]

I have one of these trimmers my self. In my opinion its an overly complicated 2 stroke engine but it does the job fairly well how ever I do think they should have just stuck with the 2 stroke design.

[@christopherlehman4045]

It’s a low emission engine

[@BrianBourgeois-]

Thank the epa.

[@johncombs6543]

I’ve never owned one. After I learned how they worked. I felt like too many corners were cut on the design of this engine. Do these last as long as the 2-cycle? Just asking.

[@nunyabisness4300]

My experience is yes. They are as durable as a two stroke

[@jv-man3698]

Wouldn’t a valve not sealing correctly, cause the whole engine to ignite, considering gas and oil are everywhere inside?

[@skirtdevil]

well done,,,,Great video!!!!!!!!!

[@jcolbyt82]

You have to wonder how many of these 4 stroke fuel/oil lubricated engines have been seized up by people running straight gas with no oil because they know damn well you don’t put 2cycle oil in a 4-stroke engine!!! “See, my weed eater is running just fine. (Shortly after that statement) damn it!! My weed eater died and I can’t get the pull cord to budge! It’s almost like the engine has seized. It’s brand new! Where the hell is the oil dipstick? How do you even add oil to this thing???” That’s probably a common string of sentences that these “dipsticks” end up saying when they lock the engine up tight. Thanks for the explanation. I knew they were lubed by 2cycle oil. I followed stihl’s directions for the fuel. I just couldn’t figure out how the valves were lubed and how the crankcase and cylinder were lubricated. I fully understand now how it works! Thanks for taking the time to make this video!

[@mike97525]

Have a still trimmer and both muffler bolts broke off😣

[@THEMOWERMEDIC1]

How?

[@mike97525]

@@THEMOWERMEDIC1 just running it?

[@crossan008]

Great info! have you ever seen the valve seat turn into chunks and ruin the top end? 🤣 I got a parts machine and that was the issue.

[@adambatchelder4121]

So you could say the 4 mix is the worst of both 2 and 4 stroke designs. Isn't the 4 mix really a emissions driven design? I remember when honda went to plastic camshafts in their little 4 stroke motors and instantly started calling them their GC motors and their old good push rod motors became commercial grade .

[@jeffewing2385]

Part number please for the new cover!

[@stevenlefebvre2991]

Thank you for explaining how this engine works. It does not seem very durable. I don’t see the advantage Over a normal two stroke.

[@motoman5023]

Very educational 😁

[@AltonRowell-gb1lb]

Interesting stuff thanks 👍

[@staceysparling8364]

Great video and explanation. Thanks!

[@benjaminleslie3155]

I thought you went through this and explained it already but I guess some people can't take the hint.

[@THEMOWERMEDIC1]

Ive never explained it

[@benjaminleslie3155]

@@THEMOWERMEDIC1 I mean the fact that the engines run on 50:1

[@jackearnest6895]

That video was very helpful

[@denniskaiser4903]

Why do they call it four mix is there a certain type of oil made for it?

[@aldoclausi3955]

2 cycle air cooled oil.

[@tier3rd375]

The name 4-mix comes from the fact that it's a 4 cycle engine that runs on mixed gas and oil.

[@mddale]

So educational.

[@jamiecrisp5084]

Great video MowerMedic 1 the 4 mix engine is just a 2 cycle engine higher torque having a camshaft, valves, push rods and rockers like a 4 cycle engine minus the oil sump STIHL did this to save on weight at 12 pounds total weight if it were a straight 4 cycle engine it would weigh 14+ pounds I've heard ECHO overseas has a 4mix trimmer called an SRM 3610T it sounds like a STIHL when running and looks like the SRM 3020 very interesting trimmer.

[@THEMOWERMEDIC1]

It’s not a two-stroke !

[@johnkosheluk1041]

And thay run long timer line and get the engine hot and melt the cam lobe

[@j.m.3731]

Look at the gas cap. fuel +oil

[@francislang5075]

well said

[@ricksanchez3176]

Short recap, some say heart disease is the leading cause of death. However EM-PLOY-EEZ are the leading cause of heart issues. *and anuerisms

[@burgerbirger2221]

Good vid :)

[@jc-d6179]

So 2 points of failure. Forget to put 2 stroke mix in or get an air leak. Genius!

[@davidward8682]

I am sorry mowermedic but what is the thinking on this system. Don't see the point of them

[@THEMOWERMEDIC1]

More power, more torque, better performance.

[@errolpoxleitner7901]

It had to do with emissions.

[@waynemanning3262]

Turn a normal 4 stroke on its side and see how long it lasts with no lubrication

[@neonjoe6180]

Think I'll stick with ported piston Thanks

[@johna.s.3847]

That would be a bullet proof engine if the cam was made out of brass or strong metal and needle bearings were installed in the wrist pin. That would be bad for Stihl since the engine would last forever.

[@Trumplican]

those things are junk. the bigger models have a bushing instead of a wrist pin that wears out too. Was this 4 mix an attempt to get 2 strokes to run cleaner?

[@snoopfurlow1275]

I agree,iam sticking to their 2 cycle or a split shaft models .they ain't nothing but problems

[@fenceman53]

But mower medic a motor that you mix gas and oil does not have valves and push rods! What is going on here? (just kidding)

[@p.istaker8862]

You can.always count on the Germans to unnecessarily complicate something.

[@nickwf70]

Too much vibration for a hand held tool, mine was always gutless, valves need adjusting alot. Other than the improved emissions....junk.

[@tonyfree2691]

Calling it a hybrid is promoting confusion! It's just a 5 stroke that's all. It's minus a sump and oil pump so, oil in fuel . Simple.

[@RobertKohut]

Weird engine... :-)

[@GWAYGWAY1]

Stupidest design fault is the camshaft is PLASTIC it melts the faces and wears down.

[@brianmcintee6647]

its a two stroke with valves

[@THEMOWERMEDIC1]

Incorrect it’s a 4 stroke with 2 cycle crankcase

[@markclark1605]

Two stroke engines don't have a camshaft, valves, push rods , valve springs.

[@jcolbyt82]

It’s a 4 stroke with valves. Lol. Two cycle engines can and do sometimes have valves. Mainly huge diesel engines on train locomotives and some large ships with diesel engines. Those engines use powerful roots blowers driven by the engine that scavenge the cylinder of exhaust (intake and exhaust valve are open at same time briefly, after the exhaust valve opens up first) and then charges the cylinder with pressurized intake air (exhaust valve closes just before the intake valve closes). The roots blower is like a supercharger. Listen to a train locomotive go from idle to a low amount of throttle and you’ll hear it spin up. The weed eater engines are true 4 cycle engines. They do an intake stroke, then a compression, then combustion, then exhaust stroke. It’s not like a 2 cycle at all. The only similarity is the fact that it gets its lubrication from oil that’s mixed in with the fuel and not from oil in a sump.

[@THEMOWERMEDIC1]

They don’t? Then I guess you’ve never heard of a Detroit diesel engine.

[@HOODLIFTER]

You are absolutely, positively, guaranteed for sure, without a shadow of a doubt, 100% wrong. That 4 Cycle-storke engine take ALL its air from the intake valve, just like any other four cycle engine. Adding oil to the gas mix is for lubrication, and oil chages then are no longer needed, It looks like it was NOT even leaking oil. That hole will ONLY vent crankcase pressure, and WIll not stop that engine from running. I did not bother with the rest of the video. My resume? Bumper to Bumber mechanic, With a first level of on road and Marine Diesel technology teaching , wich was issued to me by Career College Association. Cummins; Detroit Diesel:Caterpillar, and International Harvester factory schools.

[@THEMOWERMEDIC1]

I just let them be douche bags

[@seabass22]

What a douche

[@waynemanning3262]

Fred has probably never looked at one of these engines in real life

[@jcolbyt82]

If you truly have the credentials that you claim to have, one credential that you have demonstrated that you do not have is the complete lack of understanding as to how these engines work. It’s obvious you aren’t a Stihl engineer because if you were you would understand that what you said was 100% wrong! I mean do your research before you get on here and blast the maker of this video for giving out false information. Hate to tell you but the maker of the video is the one that is correct. Want to know how I know that??? Because I have read a Stihl service manual that explains exactly how the lubrication/fuel system works. I’m sure you have read many service manuals for the large engines that you have worked on. My advice is for you to read the Stihl service manual for this type of engine. It will help you to avoid making another mistake like this again and help keep you from looking like a fool. Your credentials mean nothing to anyone when you demonstrate that despite your certainty, you have no clue what you are talking about. Check your info before you start leaving comments on here. In this case you are completely wrong. You acknowledge that it uses 2cycle oil for lubrication. If there is no oil sump and the fuel oil mix is providing the lubrication, tell us how are the valves, rockets, and pushrods going to be lubricated?? If that hole is only a vent then the valves are going to be awfully dry. But as I said, Stihl themselves explain in their manual that the valves are oiled by the fuel oil mix coming up through the hole and into the valve cover area. Unless you claim to know more than the engineers that designed and built the damn engine and the people that repair them, you don’t know what you’re talking about.