Big chainsaw troubles..... help needed

[basod]

I put the flywheel back on (you can still see where the key was), and torqued it down, and it fired up. My question now is - is the key critical for power transmission, or is it strictly for timing? My guess would be that being a tapered shaft, that the key is primarily for timing but still am not certain. The key was cast right into the flywheel.

When it loosened up it wiped the key off the flywheel? I'd think the casting/machining would make it difficult to cast a key into a flywheel(could be wrong)

New flywheel is $76 here
http://www.partstree.com/parts/?lc=husqvarna&mn=365 Special EPA (1999-11)&dn=082960011

It's an M8X1 nut which I believe is 28-32N-m torque spec
If the flywheel moves it'll be the equivalent of an engine "jumping time"
Except this one's spinning at what? 12k+ rpm - Hopefully there's enough safety margin built into the jug/casing to hold it together

 

[MasterMech]

I'd think the casting/machining would make it difficult to cast a key into a flywheel(could be wrong)​

That's the way many small flywheels are made now.

Hemlock,

I wouldn't attempt to run the saw again until you get a replacement flywheel. The current flywheel will most likely shift position a bit every time the saw accellerates/decellerates and while starting. I would order a new flywheel and make sure the nut is torqued to spec. Definitely do not use loc-tite on that taper, as that will make future removal unnecessarily difficult.

 

[nate379]

I'd just cut a keyway into the flywheel before spending $75 on a new one! If you aren't setup to do it, bring it to machine shop with a case of beer.

 

[Ashful]

I'd just cut a keyway into the flywheel before spending $75 on a new one! If you aren't setup to do it, bring it to machine shop with a case of beer.

... also has a lower likelihood of shearing again, if you use a standard key in the new slot, versus a casting.

 

[MasterMech]

... also has a lower likelihood of shearing again, if you use a standard key in the new slot, versus a casting.

Keep in mind that the shear strength of the key just may have been engineered into the saw to prevent excessive energy from being transferred to the crankshaft in the event it comes to a very sudden stop. (although such an event would be rare on a saw.) If I were to cut a keyway into the flywheel and locate or make a suitable key, it would definitely be an aluminum key.

 

[mikefrommaine]

There are plenty of flywheels available on ebay for < $35. I'd just replace it and be done worrying about it.

 

[hemlock]

Ordered a new flywheel. Should be here in a couple of days. I ran it for an hour or so with the old flywheel, but it made me noervous. I think it was going slightly out of time. It dieseled after shutting it off when I went to refuel.

Edit - of course, now I can't get the old flywheel off. Is feathering it with a torch a bad idea?

 

[MasterMech]

Ordered a new flywheel. Should be here in a couple of days. I ran it for an hour or so with the old flywheel, but it made me noervous. I think it was going slightly out of time. It dieseled after shutting it off when I went to refuel.

Edit - of course, now I can't get the old flywheel off. Is feathering it with a torch a bad idea?

Wedge it with wooden wedge driven in snug and back the nut off 1 turn. Give it a good sharp rap with a hammer (The nut should be in position to protect the threads and the end of the shaft.) and it will pop loose.