See if there's an obstruction around the brake band or between the band and the clutch drum. Could be causing friction as it goes round.
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The chain rides in that wear groove, and as it rotates the bottom tang is rammed into the backside of the next tooth, and pushing, pulling, rubbing etc., and will quickly stretch the new chain. It will get a bit smoother when the chain is broken in, but as you use it, it will need adjusted often.
Remove the bar and chain and rev it up. See how it behaves then.
Edit: you've already done that.
Edit: you've already done that.
Cool, I’ll do that. Looks like I’ll have to start disassembling the clutch to get at it, correct?
If you have a compressor you could just blow around it.
Don’t have one handy unfortunately
SteveSr
Addicted to ArboristSite
That sprocket has some wear on it but I don't think that it is your total problem. You need to pull the clutch drum and check / clean / re-grease the clutch bearing. Also need to verify that the brake band is not rubbing on the drum. Drum should spin freely with the chain brake disengaged.
These saws normally come with a .325" .063" gauge B & C. Why was it switched to .050" gauge? This may cause some issues with the old sprocket if it was worn in with .063" gauge chain.
I'd remove the bar and chain and rule them out. Run it without and see if it behaves the same way.
Edit: You've already done it.
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When you took the sprocket cover off, there was a smaller cover over that spring and hardware, correct??
thomasinvancouver
ArboristSite Operative
Good idea on the clutch bearing. Could also be the brake dragging or some debris between the clutch and brake. But you did say that the sprocket spins freely with the bar and chain removed.
I had the same problem with the brand new Oregon bar and new Stihl chain. The tolerances on the bar were so tight the overspray from the paint was causing binding on the drive links. Take the bar and chain off the saw, put the chain on the bar and see how much drag there is when you pull it through.
In my case I had to run it for a while before the chain coasted to a stop instead of doing so immediately. It also was spitting black off the bar as it was rubbing off the paint residue.
In my case I had to run it for a while before the chain coasted to a stop instead of doing so immediately. It also was spitting black off the bar as it was rubbing off the paint residue.
Dennisthemenace
ArboristSite Operative
Looks like 36 on the box, ie 3/8 063 gauge, does the bar and sprocket match this? I can't decipher the numbers on the bar but I doubt it. Or else it's just too tight. It does look a bit tight in the photo
I'd recommend wearing gloves...
If you're unsure, a good way to get chain tension is to loosen things off so the chain hangs off the bar slightly & then tighten the tensioner untill the chain pulls itself up just snug to the bottom of the bar. Tighten things up & feel that tension... it should be on the slightly loose side of good. Loosen the bar nuts again & put a little pressure on the bar so as it pushes the tip up like if you were pressing on the saw in the cut (I just lean forward on it a little with a piece of wood under the chain) & tighten things up. This takes up any slack that could result in the bar moving slightly & will probably result in the chain becoming a bit tighter.
Check tension regularly with a new chain as things settle in & stretch etc
Check tension regularly with a new chain as things settle in & stretch etc
If its ever tossed the chain before, the drive sprocket could have slapped the back of the drive links with the sprocket creating a drag in the bar slot. Sometimes you have to file the burrs off the back of the drive links to allow it to move easily in the bar. Takes awhile for them to wear off, too.
That 3690 is the good new Stihl version of .325nk.
Like others have said the sprocket wear might be off a bit left/right for the new bar/chain. Also the oil pump drive is like a wire that has a notch to go in.
Like others have said the sprocket wear might be off a bit left/right for the new bar/chain. Also the oil pump drive is like a wire that has a notch to go in.
SteveSr
Addicted to ArboristSite
I have always wondered if this condition would self-correct the first time that the saw is revved up? I am always carefull to put the drum on correctly but some folks might not be.
SteveSr
Addicted to ArboristSite
One of the few things that hasn't been mentioned... yet is to mount the bar & chain without the clutch cover. That way you should be able to see any alignment issues. If the bar studs aren't threaded deep enough just add a couple of washers under the nuts.
