MS290 key sheared

[rmcphearson]

I re-assembled our MS290 (a complete tear down- long story) and the flywheel key sheared after a few minutes of use. I KNOW I torqued the flywheel nut to 28 Nm (appx 250 in/lbs). The engine is not locked up, it died when the flywheel came loose. I'm assuming the nut came loose. I used antiseez on the threads and shaft out of habit. I don't think that could have made a difference. Any ideas?

We are not spending another dime on this saw. I'm going to try it without the key.

 

[shutup-n-cut]

Lap the flywheel to the crankshaft useing valve lapping compound , clean the taper that you lapped with acetone and the taper on the flywheel , new key and torque the nut to spec. The use of antiseeze will usually call for an increase of the torque on the nut.

This is what we do on race karts and run them with no key and never had a flywheel issue , if you don't use a key then you will need to set your timing with a degree wheel .

Hope this might help you.

 

[Homelite410]

You will need a new flywhweel unless you go keyless. The key is merely an index point, the taper does the work therefore the taper must be clean as stated before.

 

[shutup-n-cut]

Homelite , you mention a new flywheel? Are you saying this because of the damage that was probably done when the flywheel sheared the key and spun on the shaft making it a nice parerweight. Personally I have yet to have a flywheel issue.

FYI love the Gen4 vise from you!!

 

[Duke Thieroff]

Stihl has a service bulletin stating that all crankshafts must be completely free of grease and grime when installing a flywheel.

Putting the anti-seize on it probably allowed the taper to not fully grab the flywheel, in turn letting it loose and shearing the key.

 

[pioneerguy600]

Stihl has a service bulletin stating that all crankshafts must be completely free of grease and grime when installing a flywheel.

Putting the anti-seize on it probably allowed the taper to not fully grab the flywheel, in turn letting it loose and shearing the key.

Bingo, anything on the shaft taper is a no no, shaft and flywheel must be absolutely clean and dry for the friction necessary to hold the flywheel in place. Neverseize , definitely not.

 

[Terry Syd]

The only thing I have put on my flywheel and shaft is 'electrical contact cleaner'. I spray down the parts just prior to assembly, it gets rid of any residual oil that I might have left by touching the parts.

 

[50blues]

IIRC the key is part of the flywheel on the 290.

 

[griffonks]

The only thing I have put on my flywheel and shaft is 'electrical contact cleaner'. I spray down the parts just prior to assembly, it gets rid of any residual oil that I might have left by touching the parts.

Brake Cleaner.....

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[Terry Syd]

I used to be an electronic technician, got used to using the stuff for all sorts of things.

 

[k_kindig11]

You should still be able to use the flywheel as is. I've used several with sheared key. It's fairly easy to see where the key was located... transfer the location to a visible location on the crank end and flywheel with a scribe, line up, and then tighten it down. As suggested, make sure crank taper and flywheel are clean.


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[shutup-n-cut]

IIRC the key is part of the flywheel on the 290.

Thanks for answering that , learned something else here.

 

[rmcphearson]

Yes the key is (was) part of the flywheel on this saw. OK, I'm going with the theory that the antiseez was the problem. I cleaned the tapers with carb cleaner and re-assembled, aligning by eye, torqing the nut to 30lbs with blue loctite. It's running for now. Thanks for your help gents!