Thought I’d revive this thread after almost 16 years.
We have a MS260 Pro on the farm. It’s rough. I think the bearings are in bad shape given the amount of movement in the flywheel and clutch (I.e. the crankshaft that both are attached to). I believe it had been converted from .325 to a 3/8 rim sprocket. That’s what’s on there now. The issue is the chain will stop in the cut with the engine still maintaining power. I think what’s happening is the clutch drum is worn away so there’s not enought friction on it to turn the drum/sprocket&chain. There’s been a lot of wear/heat in there and there’s a lip on the inside of the drum. I called the Stihl dealer and read off the part number to try to replace the drum. He said the part didn’t come up and he really didn’t have any idea on it. 1121160 2910B
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He recommended going with the standard .325 spur sprocket for replacement. I have a .325 green bar/chain I could use if I go back to .325. I suppose I could get a new chain too, more aggressive than what I could poach from another saw with that same bar. My biggest concern is throwing a lot of money at the saw when the bearings appear so bad. At some point I imagine the top end will go if air is leaking in.
The saw runs ok right now, but wondering if I run til it dies? If I want to keep running it, does converting back to .325 make sense, since I have to replace clutch drum anyway? (At least that’s what I think is wrong with it…) Perhaps it would be less hard on the worn out saw?
Im also wondering if converting it in the first place had an impact on the worn seals. It seemed like lately the chain would not pull through by hand easily, unless you really adjust the chain just so. (I’m also thinking that the sprocket gets pulled toward the nose since it’s worn out, so that could affect the chain staying in line.). Thanks as always.