Chain stretch, already?

[precaud]

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.

 

[minkota1]

Have you checked the drivers for burrs? Is the chain riding up out of the groove?

 

[minkota1]

If you have a burr, you will need to file them done so the chain will fit back in the groove.

 

[Trigger-Time]

Could have been small wood chip between sprocket a chain.
Or bar not tight and slipped

 

[precaud]

The chain is riding fine in the groove, no burrs. Can a sprocket be bad (asymmetrical) out of the box?

 

[minkota1]

I had a bent tensioner screw once that would allow the bar to move a little after I thought it was tight.

 

[precaud]

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.

 

[Frank Boyer]

Do a run out check on the crank.

 

[oldsaw]

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

 

[SawTroll]

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.

 

[mountainlake]

As Frank said, crankshaft run out or or a bad sprocket. Check the sprocket for any derbris that would keep the chain from seating all the way.. Steve

 

[SawTroll]

OK, brand new saw (Dolmar 401) and chain (91VX), two tanks ran through it a couple weeks ago. ....

Did you notise anything not beeing right then?

Anyway, if the saw is new, take it back to the dealer.......

 

[Fish]

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.

 

[precaud]

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...

 

[SawTroll]

Do what Fish said, and back to the dealer you go.........opcorn:

 

[scottr]

Do a run out check on the crank.

Precaud , this would tell if the crankshaft was straight not bent .

 

[Crofter]

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.

 

[precaud]

Do what Fish said,

Ah, the joys of an outboard clutch...

and back to the dealer you go.........

Well, not me, but the saw... no local dealer...

There sure is a LOT of play in the sprocket on the shaft - it easily moves side to side and front to back.

 

[ericjeeper]

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

 

[SawTroll]

...
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.......