Is Stihl Quality Slipping? 4-mix Engine Repair, Stihl KM 90R.

My Stihl KM-90r quit running right, and the fix turned out to be pretty interesting.

Topdon thermal imager:
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00:00 Intro & what’s wrong
2:56 Troubleshooting fuel, spark
4:40 Carb removal
6:47 Check valves & exhaust
9:20 Cam gear & timing
12:56 Topdon thermal imager
15:50 Continue teardown
18:41 Inspect cam gear & how it lubricates
21:00 Clean valves and why it failed
24:18 Fix clutch
27:15 Meanwhile…
27:51 Reassembly
30:48 New cam gear
34:28 Compression release
37:01 Adjust valves
38:45 Complete assembly & testing
40:29 Adjust carb
43:05 Opinion on Stihl
44:47 Outro

29 Replies to “Is Stihl Quality Slipping? 4-mix Engine Repair, Stihl KM 90R.”

  1. Its better to desing it that way that only 1of the parts that is pretty easy to replace gets worn. All metal construction and now you would be changin the whole valvetrain. And the Rtv cant handle normal gasoline from pump, but if you use right premix gas (aspen makes a great one) and it wont do anything to rtv.

  2. My LOL was "If I keep having trouble out of this, I might machine one out of brass. It will be heavier." 31:30
    Ok, thanks to you we now know to pull the valve cover and look at the travel.
    Little to no normal valve travel then we have a worn valve gear.
    Thanks, I have 2 of this Stihl type motors and can disassemble them into 500 pieces and fix all the problems.

  3. Do not invest in that technology. That is garbage. Fathers built a two stroke for a reason that is emissions crap!!!

  4. That plastic gear may be similar in concept as the gas tube on a AR15, it will melt way before the other parts saving it from critical damage.

  5. Good fix and all the detail into what parts are doing to drive and run it.

  6. Every time I hear someone say "Click" when not using a torque wrench it reminds me of the Awesome channel Elderly Iron. Another Great channel!

  7. i never knew theres small engines like this 😮 pretty interestign desing, not sure why just not 2-stroke

  8. What with the politics, school shootings, tornadoes, etc. etc. etc. I am giving you a pass on using metric measurements. Cheers from a metric country. ~ulrich

  9. The melted cam gear is a problem Stihl had with the 4 mix engines, the fix they came up with is a tab on the aluminium cam gear cover on the in side to direct oil to the lobe on the cam gear, I saw that yours doesn't have that tab so it might happen again. I am surprised that your Stihl dealer didn't mention anything.

  10. WHY , would Stihl add all that mechanical complexity for what purpose ? All that UNnecessary Crap when their 2 cycle engine runs great !!!!

  11. Wtf is “RTV?” or whatever you keep saying over these last 2 videos.

  12. So, watching this with my Dad and he wanted me to let you know you should be wearing hearing protection. 😀

  13. I'll have to go and check if my Stihl brush cutter is 2 or 4 stroke now. I just assumed it was 2 stroke.
    All I do is pull the cord and it goes. Since I have to premix I've never really thought about it.
    That's hilarious considering I'm an auto mechanic.

  14. The problem was that it did not have a piston return spring from the factory.

  15. Sorry am 54 and I just can't rap my head around plastic parts in a motor god I guess am old sorry all just I mean wth

  16. This reminds me… I have an Echo leaf blower to disassemble. “No disassemble Stefanie, no disassemble!” Also we’re happy the ???? made it back ????.

  17. I'm pretty early in the video but I always look at the spark arrester in the exhaust when I lose power in weed eaters

  18. That Stihl engine looks like the answer to a question nobody asked – lets combine the disadvantages of a 2 stroke with the disadvantages of a four stroke, and end up with a short lived, smokey, more complicated and heavier result. With added wearing plastic and red gorilla snot. Nice.

  19. My boss has a gas stihl blower that we use for lawn service. Bought it in 2010 and it's still working to this day it's his oldest piece of equipment it gets used 5 days a week!

  20. I like your videos but "Is Stihl quality slipping?" Is pretty clickbait considering that model was released in 2007, so this video gets a downvote

  21. I wonder if ethanol gas in the mix diluted the oil too much and the lobe heated up.

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