# Stihl MS290 - sheared flywheel key repair



## MMH (Sep 25, 2009)

I sheared the key to the flywheel key on my Stihl MS290.

Yes, I did what I shouldn't have done - was using it to hold the crank while removing the clutch. Nonetheless, surprised that the 'key' is die cast integrally w/ the flywheel. 

Anyway, I was going to try to mill/cut a keyway groove into the flywheel & use a woodruff key. Anyone else do this? Is there an easier way to fix this?


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## TRI955 (Sep 25, 2009)

You'll most likley be looking for a new flywheel. It wouldn't hurt to try your way, I guess....good luck.


Mike


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## Rookie1 (Sep 25, 2009)

There was a wise man on here named Lake that said you didnt need the keyway if all was clean and the nut was tightened properly. I never tried it but if I was in your shoes Id give it a whirl.


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## TRI955 (Sep 25, 2009)

Rookie1 said:


> There was a wise man on here named Lake that said you didnt need the keyway if all was clean and the nut was tightened properly. I never tried it but if I was in your shoes Id give it a whirl.



That is a great suggestion!!!!! I would try that. Rep your way....

Mike


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## breymeyerfam (Sep 25, 2009)

key is just for aligning. shouldn't move in normal operation without a key, as long as its torqued correctly.


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## MMH (Sep 25, 2009)

breymeyerfam said:


> key is just for aligning. shouldn't move in normal operation without a key, as long as its torqued correctly.


Based on that comment, I'll try some JB Weld. I have the part that sheared off. The crack will allow good alignment of the original position. Any JB Weld Experts out there?


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## Fish (Sep 25, 2009)

MMH said:


> Based on that comment, I'll try some JB Weld. I have the part that sheared off. The crack will allow good alignment of the original position. Any JB Weld Experts out there?



Why?


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## HimWill (Sep 25, 2009)

If you go messing around with epoxy,you most likely will make the flywheel unusable.A botched up epoxy job will mess up the taper fit of the flywheel to the crankshaft.Degrease them both,line them up and reinstall.Thump it (the flywheel) a couple times with a hammer handle to preseat the flywheel and carry on.


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## Saw Dr. (Sep 25, 2009)

If you have not started hacking on it yet, send me your sheared one, and I'll send you a good one.


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## splitpost (Sep 26, 2009)

less drama swaping out plenty of good cheap used ones around,thats what i did, threw buggered one under work bench for a rainy day.


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## blsnelling (Sep 26, 2009)

Rookie1 said:


> There was a wise man on here named Lake that said you didnt need the keyway if all was clean and the nut was tightened properly. I never tried it but if I was in your shoes Id give it a whirl.



I tried that once playing with the timing on a saw and it slipped. I had another saw with a cast in flywheel like yours that was sheared. I ran it for a while with the sheared key and it held. Unless you are that strapped for cash, I'd recommend you just pony up and replace it.


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## MMH (Sep 26, 2009)

B200Driver said:


> If you have not started hacking on it yet, send me your sheared one, and I'll send you a good one.


Thanks. PM sent.


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## edisto (Sep 26, 2009)

MMH said:


> Based on that comment, I'll try some JB Weld. I have the part that sheared off. The crack will allow good alignment of the original position. Any JB Weld Experts out there?



Remember the suggestion to not use the key works IF the shaft and groove are CLEAN!

The magnesium keys are just for alignment...they will crack if the torque on the flywheel is not right. I'm sure the same is true for the integral key.


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## andrethegiant70 (Sep 26, 2009)

I sheared a flywheel key on a Husky 41. I ground the sheared area into a pit, snipped a finishing nail to the right length and put it in the slot. On it went, torqued down well. The nail helped line things up and kept them aligned in case the flywheel had any propensity to slip. I ran it that way for a few years. I can't say this is the right way to fix things, but i did it in a pinch just to go cut some wood and it ended up being very secure. The only down side seemed to be that if I ever took off the flywheel I would need to repeat the process. 

I ended up coming across another flywheel for cheap (off a busted Poulan) and replaced it before I sold it. If you don't plan to have the saw forever and plan to sell, you're going to have to replace it in the long haul. Why not just get it over with?

One factor that may influence you is rotating mass. The 029 flywheel is considerably larger than a 41. These things are the most likely to sheer when the engine stops hard.. the flywheel wants to keep going. Sir Isaac indicates that the larger the mass, the more effort will be needed to stop it when it's rotating... a big flywheel, like that on the 029 will be more likely to spin than a 41.


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## Saw Dr. (Sep 26, 2009)

I got him set up, guys.


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## edisto (Sep 26, 2009)

andrethegiant70 said:


> I sheared a flywheel key on a Husky 41. I ground the sheared area into a pit, snipped a finishing nail to the right length and put it in the slot.



There's a reason they make the keys soft...but I guess if the flywheel already was buggered, it doesn't matter much.


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## cdguck (Jul 16, 2018)

Hi guys, I know that this is an extremely old thread but I wanted to say thanks for all the good advise provided here...and then we can let the thread die again.

I have a Stihl 032 AV that I picked up for $30. It was non-running and filthy, but had very little use. The guy who had it couldn’t figure out what was going on and didn’t want to mess with it. Checked the piston and it was spotless. Long story short, it sheared a flywheel key and that thing was not coming out. I got frustrated and let it sit for a couple years. Ran across this thread today and thought I’d give these suggestions a try. The flywheel was dirty and scored. I filed the flywheel key flush, cleaned both surfaces really well, put some toothpaste on it, gave it a little tap to secure it, blocked the piston from moving and torqued it down. Put everything back together expecting to put it back on the shelf for another couple years...couldn’t believe it when it fired right up and it runs like a champ.

Thanks again, even if this was from 9 years ago.


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