Great troubleshooting! Very interesting...

When you said “mechanically impossible” I was like yeah unless the valves float lol... then you came to the same conclusion that’s awesome! 4 mix stihls seem pretty reliable but I like my 2 stroke echo equipment because they don’t have stuff like this happen.

That was some fine troubleshooting with a simple fix. Your explanation of events leading up to problem is perfectly understandable. I have experienced valve float in 60s muscle cars back in the day.

I do believe your professional opinion is correct sir . That was an interesting video.

I always like a good puzzle, and I like how you solved it!

Nice work, and spot on about not being able to wait for warranty stuff sometimes, customers have to earn to pay for repairs

I’ve owned one Stihl 4-Mess. That cured me of ever owning another. My Shindiawa and RedMax units just work.

You sure run onto the wild problems. 👍

Thank you, now I'm warned about a possible problem on my 4 strokes engine. I didn't know Stihl had 4-strokes.

Wow having the proper diagnostic tools for sure diagnosed it real quick! Customer being honest, helps too! 🇺🇸🤙🏻🔧🦅

Those workers that dld that, keep them around.. 1) They get the work done 2) They make you look like a GENIUS

I have a 17 year old Cub Cadet trimmer. I prefer Echo over it, but it still runs strongly to this day. That tells you something about Stihl!

Seen this before and wondered why it happened. Now I know. Thanks!

I think you are 100% correct in your valve float theory, that is the only way this could have happened, grossly over revving under no load .

We are lucky in my town - the main Stihl dealer is a small machine shop. The one employee is also the owner. If you take something back for warranty work, you get it back the same day. The next day at the latest. There are a couple other dealers in town, but they don’t even do their own repairs. Our guy won’t repair their stuff. If you bought it elsewhere, take it there to get it repaired. I understand that he is a Stihl dealer, but he has the luxury of being able to send those who bought elsewhere packing. I don’t blame him.

Great diagnosis. Keep up the great work and videos

By shear chance the first trimmer I ever used was a Husqvarna. That machine served me so good (and still does) that I fell in love with the brand. When I opened my small land care business there was only one trimmer that I considered. Of course I bought 2 additional Husqvarna's 525 RX. I will be honest and tell you that I haven't serviced any of my 3 Husky trimmers, not once, in the last 4 years that I owned them and used them heavily. The sparks are the same, the air filters - original. Nothing. I always used their oil and had absolutely no problems with them.. I suppose Stihl is a great brand but I would advise everyone to buy Husky and be set for a life.

I just saw the exact same problem in a 4mix. This one however was eight years old and had NEVER had the valves adjusted. So there was WAY too much lash on the rocker arms and the second he turned it on its side it died.

That only happens with neglecting owners that run them wide open... Valves start floating (sounds like rev limiter) then a rocker pops off or she drops a valve. Simple. Operate the equipment correctly I have a 15 year old stihl fs100rx 4 cycle. Runs perfect still. I still cut yards/only ever had to replace the clutch Camshaft Air filter And plug

I have a Stihl FS 81 that my Dad bought probably 30 years ago and it is still running strong.

Once Again.You Hit A Grandslam. Richard.

I've got 2 FS130Rs I'm working on for my municipality. The intake valve did the same thing on one. I adjusted the lash and restarted, did it again after 20 seconds with no real revs. The cam lobe looks like garbage but I also have reason to suspect carbon issues, as the engine sort of want to bind at TDC even with the cam removed. Good to know this is a common problem, as I'm not to inclined to stihl's more radical designs.

I agree.. very interesting insight on what happens when Dude's are working out on the field. That said I am not too happy with the new 4mix Stihl engines. The 2 stoke design was perfect enough

Awesome diagnosis! Impressive.

Great trouble shooting and explanation Jeremy!

Great Call Good job figuring that one out

Good job figuring it out

Great sleuthing! Also, I had never heard of these 4 Mix engines, so you sent me on a search to learn a little more. Thanks!

I have one where the thin metal plate behind the cam gear had a piece come off, found it's way to the intake valve and hung it open...stopping the engine. Then when trying to restart, it got into the cylinder and dinged up the piston head. Other than that thin metal disc, the design is simple and sturdy

Good job and tutorial yet again!!

Thank you for running the engine at the end.

My goodness thats a brand new piece of equipment this is the reason i stick with echos in the 35 years that i have been in buisness not one echo has let us down even some of our little srm225 units that are 8 years old that are used 5 and 6 days a week none stop here in Miami fla are still going strong thanks for sharing.

Had the rocker arm come completely off the valve stem on a brand new BR800. Put it back on, set the valves and it's been running perfect for about a year now.

Awesome video. Great diagnosis! The pros are tough on their equipment for sure.

Very common I don’t even start a new one without setting lash myself they always seem a bit loose from factory in my opinion

That was very interesting! Thank You for sharing this video.

Could also be a weak valve spring. Not all valve springs are created equal even when new.

Nice work 👍 He's so lucky that piston didn't smack that valve.

Great info Mowermedic1 with that being a 4 mix engine it has no governor like standard 4 cycle engines so it uses the weight of the cutting head and the resistance of the string to govern the engine speed i would be scared to see what the peak rpms were when that happened.

I do not like any 4-cycle tiny engines, 2-cycle any day for many reasons

I actually took one of my Honda Mowers in to have it looked at because it wouldn't start. Note, it started and ran fine at one job, loaded on the trailer, and was going to mow the next backyard because again, my zero turn wouldn't fit through the customers fence. It wouldn't start to save my life, Thank god i have two of these mowers. I took it in for service to have it looked at to see what could have happened. I was told by the mechanic from John Deere/Honda that the engine had zero compression and a new engine would cost more than the mower and it was toast. Just seemed very odd him saying that when it ran perfectly fine the last yard i did with it. I got to looking on the mower and noticed and thought, Did the front of my Honda bang against something in the front, dual overhead valve on the Honda and the cover is easily bendable. I thought and looked and it looked slightly bent in like it had banged into my big mower while it was on the trailer. I took off the OHV cover and beat it straight with a rubber mallet to make sure the valves had plenty of clearance and sure enough after putting the cover back on after straightening it, It fired up first pull just like it always did before. Honda HRR 216 19 year old mowers and i love them.

Great video! Question. What is the secret to getting those carbs off without feeling like I am going to break something? I have to force them off and on every time. I know there has to be something I'm missing...

Excellent fault finding diagnosis and explanation.

Pretty impressive diagnostics. Makes sense.

Another tid bit of troubleshooting information to be included in the Operators Manual....! Good diagnose !

Love the K5HL in the background

Great info Jeremy, I'll use this in my backyard shop brother.... thank you :)

One's demise is always one's own making. I knew immediately it would be user error

I'm surprised the customer didn't damage a valve and or piston. 🐯

Great explanation of valve float!

Great diagnosis! 👍👏🔧🧰

Man, 12hrs of straight trimmin!!

very good info and pics of the problem

STIHL has a great reputation along the years. The only problem is the brand. It is like FORD F abrication O rdinary R epairs D aily

Yo yo cupcake 🧁. A good video.. I am working on am old fs90.. given me some head scratching lol .. hope all is good

Great diagnosis

Great Video Medic!

Two strokes still rule!

Tappits are a nightmare with Stihl still wouldn't use another brand. I remember KM90s back in the day bent and snapped tappits all the time unless they were adjusted every couple of months. They did also get 12 hours use a day though.

People dogging the 4 mix don’t know how to maintain anything with valves 😂 these things will run for ever. Way better low end torque and smokes the 2 strokes

You're an absolute genius 👏 🍕 Give this man a Pizza You have a great understanding of the guys in the field 👍 and boy do you know stuff... 😉 Thanks 🙏🏼

Love the train sounds.

Interesting stuff. Thanks for the information.

Good fix.

Valve Float plus Gravity equals No Compression. In this case.

That was a crazy one.

Thanks. Great video brother

That's why they pay your the big bucks my friend

Isn’t That an Interference Engine How Did The Valve not Hit The Piston 😮😮😳 That Was Lucky 😀😊 Great Diagnosis

Stihl advertises and sells a lot of equipment- yet few OEM parts on line and many times on-order at a dealer. How do you run a business if there's no support for the product?

You Da MAN

Berry, Berry Interesting!

Wow.. Good catch ..

Thanks for the info mate ,jimmy Australia

I like the echo stuff better.

Thank you Mr man

The reason it landed on the valve stem is due to the fact. The rocker arm was to loose. Therefore when the customer turned on side full bore revving. Rocker arm shifted to another seat

You are th Sherlock Holmes of small engines. Speakin of rich oil mixtures: I just bought a 111 trimmer. It was new and they gassed it up for me. I cut grass and weeds for a few hours and realized I needed a brush cutter. I put the trimmer up for a week and the next wknd put 40 to 1 mix in it instead of 50 to 1 as recommended. Why did I do that? Well, that's what I had mixed and the folks I bought it from indicated that it would probably work. Unh unh! Couldn't get it to fire. It seemed like I had so much compression I couldn't get it to turn fast enough to fire. I drained the 40 to 1 let it dry out. Put 50 to 1 in and after a few pulls she cranked, smoked for a few moments and has run fine since. Does that make sense. Is it the case that a Stihl is so tight it won't run on 40 to 1 or is the carb unable to do its magic on the air and the mix with that much oil. Help me out here.

Great vid

Excelente Solución. Te cuento que yo tengo una FS 111 y la pregunta es: Como se hace el cambio de aceite del motor?

Wow thanks for the great information very informative

To me it's all about proper maintenance

They should be running a standard 2 stroke model without valves. Either customer did not inform sales person on how they would be used and for how long daily, or sales person did not listen or is an idiot.

I remember years ago a friend had a two stroke line trimmer that would not start and had very low compression. It turned out to be a blocked exhaust. Mason bees had built their nest in there while it was unused for a few weeks. Had me scratching my head for a wee while until it fell over on the bench and I noticed the blockage.

Nice video good job 👍

Stihl oil the synthetic ethanol free gas or canned gas they run forever until the untrained user does something stupid 💪

Interesting for sure!

Pretty sure that's what happened to mine. The cap flew off

Thanks for video

If that was an Echo it would still be out there cutting no question !! When will folk learn ???

Great video!

Makes sense to me 😊

Hey buddy is there anyway you can put down what’s the valve clearance on the trimmer thanks for the input blessings

Hi there, where I come from we say Stihl(Still) not Steel for the brand.

good info , thank you sir. Good job!!

Hi, Have you done a video on performing a leak down test on one of these 4mix engines?

Question the white part below you thumb, that connected to throttle, what is this called please?

Great info.

Good stuff! Thank you!

Great information thanks