stihl 025 chain tension

[JONSSTIHL]

I have a funny problem with the chain tension on my 025. If I tension it properly so that the underside of chain is touching the bar, when I pull the chain along by hand to check if it moves freely there is a certain spot that comes along about every 4-6 inches of pulling the chain where the chain is slack and doesn't touch the bottom of the bar. is this normal.

when I get home tonight I'm going to pull the sprocket and clutch drum to see if the little bearing on the crank is toasted but it seems to run well.

any one have any ideas. the saw runs too well to have a bad crank bearing at least I think.

 

[Dolmar4life]

sure there isnt a chunk of crap wedged in the tip roller?

 

[sawinredneck]

Are you sure that the chain is seated in the sprocket correctly? Any number of things could be going on, I hope that the clutch bearing is bad, cheapest option. The roller tip might be bent, not likely though, you might have a bent crank as well, very expensive!! Hopefully one of the others will chime in with another, cheaper thought as to what is going on! Good luck!!!
Andy

 

[Ombesb]

I am no expert on any of this, but I have noticed that on both of my smaller saws, one nearly new, so not worn or bent. I am sure someone tht really knows something will come along , but I think it is the timing between the teeth on the sprocket and those of the tip. Be curious to know for sure myself??

 

[bump_r]

Any links sticking and not rounding the sprocket(s) cleanly?

 

[Dolmar4life]

bent crank wouldnt change the chain tension unless it was running...or you pulled the recoil while spining the chain..

 

[Ombesb]

Not sure about Jons saw there , but on mine... echo346, I have done the full mechanical check, crank not bent, sprocket bearings ok, bar straight, nose good. I can run the chain around by hand on the bar , off of the saw , with no snags at all. But on the saw it has spots where it gets tighter , then a bit on looser. If pulled along rapidly the average is fine.

 

[Dolmar4life]

burrs on the edges of the drives can make that happen also..

 

[Butch(OH)]

You have an out of round sprocket on one end or both. Not an uncommon occurance, at least on the saws I have. Out of 15 saws most of mine do it to some degree. The issue bars on the mid grade saws seem to be the worst as do the spur type drive sprockets. Tighten the chain to the point that it doesnt drag hard at the tight spot and run it. As things wear in the problem will go away slowly.

 

[Ombesb]

I do believe that is in fact correct. I ran down to look at the chain carefully as it went around, marked a tooth on both ends. It was a little snugger at all times on one tooth on the bar, and at times a bit more than that. Didn't take the timeto do a careful measurement on tooth depths but I think that there are higher teeth on both ends that when they line up going into a link becomes the 'tight' spot. And this is a little low end saw , hence bar also. The bigger saws have better bars and do not do this. Plus , I would think, anything with a rim and drum would have just a touch of play to hide any higher teeth.

 

[wagonwheeler]

Would the wrong pitch chain cause it to climb and fall on the sprockets causing the varying tension?

Chaser

 

[Ombesb]

Would the wrong pitch chain cause it to climb and fall on the sprockets causing the varying tension?

Chaser

Yes it would , but that would be a gross amount of difference, I'm only talking a few thousands here.

 

[JONSSTIHL]

thanks for all the replies,

I haven't had a chance to check things out but I'm a little less worried now because with your help I realized that it can't be the crank that is bent so at least it shouldn't be too expensive to fix.

the bar chain and rim sprocket + drum are all new only about 2 days work on them so I am hoping it is just crap stuck in the sprocket