Chain stretch, already?

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precaud

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OK, brand new saw (Dolmar 401) and chain (91VX), two tanks ran through it a couple weeks ago. Adjusted chain in prep for tomorrow (1st pic) then rotate it a few inches, and major sag (2nd pic). Can only be chain stretch, yes? Will this equalize out in time? I've never seen this before on a new chain.
 
Well it appears to be the sprocket. I moved the chain to a sag point, marked the sprocket rim against a reference point on the saw, and every revolution of the sprocket, when it gets to that point, the chain sags. Grrrr.
 
Make sure the nose of the bar isn't dropping on you. It will look like the chain is stretching, but really it's just because you didn't keep the bar up when you tightened it up.

Mark
 
Make sure the nose of the bar isn't dropping on you. It will look like the chain is stretching, but really it's just because you didn't keep the bar up when you tightened it up.

Mark


My first thought, also, unless something is seriously wrong .........

I have heard of out-of-round sprockets before, but then you should have noticed it when using the saw the first time.

One thing is sure, stretch is not the culprit here. ;)


Anyway, new chains is more prone to stretch than old ones, and should be "run in" properly.
 
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remove the bar and chain, rotate the chain over the sprocket and watch,
do the same with the bar sprocket, you will likely find one is the incorrect
pitch.
 
Oldsaw: the nose isn't dropping.

Frank Boyer: I'll show my ignorance... what's runout?

SawTroll: To be honest, I didn't inspect it that carefully when I was out in the woods with it a couple weeks ago, except for stopping mid-tank to adjust out the slack expected from a new chain...
 
checking the crank runout is valid but in this case the lumpety hump comes with moving the chain and sprocket which is not rotating the crank, only clutch drum and sprocket. I suspect Fish is correct; faulty or incompatible sprocket.
 
sounds like spur gear or bar sproket tip

Sounds to me like he is only turning the drive gear not the entire crankshaft. That in itself would eliminate the bent crank theory.Yes?
If he is just pulling the chain along by hand, he is not rotating the crankshaft.
So either a 325 on a 375 or a hunk a crap in one of the sproket slots
 
...
There sure is a LOT of play in the sprocket on the shaft - it easily moves side to side and front to back.

There should be play sideways, if it is a rim, but not front to back - sounds like the rim is for a larger spline than is on the saw.......:mad:
 

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