Chain stretch, already?

[Crofter]

Do we possibly have the issue of a mixture of low profile and regular profile components?

 

[precaud]

Don't think so.

 

[PES+]

You would not be able to discern much by measuring the spur it would be a matter of the spur sprocket not being mounted on center of the drum.

Do you have another chain? I looked back and no one has mentioned trying another one yet.

And could you take two pictures like the first two you posted but show the tip so I can see the way the chain is matching to the sprocket nose rails.

It does make me wonder that you mention that you can detect some bar tip sprocket movement/lobing

 

[AZLOGGER]

precaud:

The chain you mentioned 91VX is low pro 3/8, check the spur and bar and make sure they are both 3/8 pitch. It sounds like one of them might be .325 pitch and this will cause the problem you are experiencing. I have seen this problem before, when customers try and fit the wrong chain on the wrong bars. :bang: :bang:

 

[romeo]

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.

It will stop stretching eventually. Its not usually noticeable with chainsaws but when we run new chain on the bikesaws they can stretch more than an inch in 10 seconds of cut time.
Make sure your chain is oiling if you think its getting to hot. I like to use a piece of cardboard, point the bar at it keeping it about 1 inch away and open her up. If your oiling you will leave a nice oil stripe on the cardboard. No stripe no oil.

 

[scottr]

While I'm waiting for the dealer to reply... I examined things more closely last night and the slop is not all caused by the drive sprocket - some may be in the nose spocket also. So I got out my caliper to measure variations in the spurs.

I'm not clear about what variations I should be looking for: in the height of the spurs, the width of the spurs, or in the depth of the valleys between them? (Feel free to correct my terminology...)

I would look for the height of the spur tooth since there are no wear marks on the spur . You'd have to take the drum/spur off to measure from inside the hub to the tip of the spur tooth . Maybe you could measure from the bar stud to the tooth and not have to remove the drum/spur .

 

[precaud]

Good suggestions Scott - I'll check em out after work.

 

[SawTroll]

According to this IPL, the standard sprocket is .325, and spur - but there could of course be variations for different markets etc, so it may not be relevant.........

 

[precaud]

PS-401's for the USA market come set up for 3/8" low profile.

 

[Crofter]

Standard 3/8 and 3/8 Low Pro are not exactly the same shape of sprocket whether drive or bar nose. The issue of being tight one spot then loose when moved a few inches along, is not simple chain elongation from wearing in. A .325 and a small 3/8 low pro sprocket are easy to confuse.

 

[SawTroll]

.... A .325 and a small 3/8 low pro sprocket are easy to confuse.

..but the .325 ones usually are 7-pin, and the 3/8" lo-pro ones 6-pin, on really small saws.

 

[precaud]

According to this IPL, the standard sprocket is .325, and spur - but there could of course be variations for different markets etc, so it may not be relevant.........

The .325 sprocket is standard on the 410 and 411 models, not the 401.

 

[SawTroll]

The .325 sprocket is standard on the 410 and 411 models, not the 401.

Oppppppssss....umpkin2:

...you are right, I misread it.......