Dolmar 6400 Can't spin chain backwards?

[banditt007]

I have a 6400, and although I bought it a couple years ago there has literally been about a tank of fuel through it, everything I've run into since has only required small saws...Its running carlton chain 3/8" .050 and an 8pin sprocket, and a 20" Total super bar.

Anyway to the question, on my other saws (echo cs450/homelite 33cc cheapo) when the saws are off and the chain brake is not engaged, I can rotate the chain in both directions. On my Dolmar I can rotate the chain in its cutting direction no problem, but when I go to spin it backwards it only moves an inch or two and then something feels like its binding and stops the chain from going further. What/why is that?

Its seems like who cares if it spins backwards-when the chain jams on the bar and you throttle up but the chain doesn't spin, I always just put the bar on some wood and pushed/pulled to free it up. I don't want to screw something up if its binding.

One other thing, when adjusting the chain tension, If I ever tension it a little too much, and then want to slack it up a little, its like the adjustment screw binds up and I need to force it to get to turn back to slack up the tension. Seems kind of a not so great tensioning system...

 

[woodbuckin]

You should be able to spin the chain backward. Clutch binding up maybe when rotating backwards? If you take the bar and chain off can you spin the sprocket in both directions easily?

Have you owned the saw since new? Adjuster should be pretty easy to operate... something sounds amiss.

 

[banditt007]

Yes owned since new...So the first post I did was based off of memory from about a year ago... With that said I just took the chainsaw out and started messing with it. To begin with, forget the chain tensioning thing for now, I tried to replicate it and I can't. Only thing different was last time it was summer time (80F+) and now the saw is about 50F. Either way as of now everything there is working fine.

Onto the chain binding thing. I took the bar and chain off and the clutch drum spins perfect both directions, no problems there. I put the chain on the bar and mounted it to the saw with just the nuts (no clutch cover) and the chain spins both forward and backwards. With the clutch cover on, the problem resurfaces, with it binding when trying to go backwards. On a whim, I replaced the 8pin sprocket with the original 7 pin, and now when the saw is all ready to go, the chain spins both forward and backwards as it should.

So it seems the repositioning of everything with the larger sprocket is causing some sort of interference with the chain and clutch cover. Funny thing is going forward feels just the same as with the 7 or 8 pin sprocket, but the 8 binds in reverse... I'll have to look into it more.

 

[Conquistador3]

Try spinning the chain by hand upside down under a floodlight with the 8 pin sprocket to see where the chain binds. If you still don't see anything try borrowing a borescope or buy a cheap one from China (after they are back from the Lunar New Year vacation) and send it inside the clutch cover. Also visually inspect the clutch cover to see if there's any sign of the chain catching in it.

I am no Dolmar expert, but I suspect you were sold a sprocket that fits the 6400 but is not really compatible with it.

 

[CR888]

Non-issue. Chainsaw chain is only supposed to be moved forwards...not backwards. Both drive tangs & sprocket wear from the chain moving in the correct direction, once you reverse that its no longer a smooth transition between chain & sprocket. If you really think this is important fit a NEW chain & NEW sprocket and go at it until your hearts content. FWIW, the only thing you'll get out of turning the chain backwards is CUT FINGERS!

 

[woodbuckin]

just a thought.... diameter of the 8pin sprocket is larger than the stock 7pin. check the rubber chip deflector for interference?

 

[Huskybill]

Is this on a thick side and thin side rim? Maybe in backwards?

 

[buzz sawyer]

I run 7 t on mine and have no issues with 20" 24" 28". Sounds like could be wear on the sprocket as CR888 said.

 

[banditt007]

Chip deflector has already been trimmed, again no problems clearance going forward...all parts have about 2 or less gas tanks through them. 7pt sprocket is Oregon brand, 8pt is Archer brand. I replied to everyones posts and then lost my reply.. with that said I tore back into this thing, I took a caliper and measured both sprockets, from the outer faces to the center of where the drive links go is even on both sides, both sprockets. The Archer brand is about .010" thicker overall. Seemed as if mounting the sprockets either way would make no difference in how the chain would align. I always ran both with the writing to the outboard. However after looking at both sprockets the Oregon looks pretty much symmetrical, however the Archer brand has vent holes on one side, the other side does not. I had been running the 8pt Archer with those vent holes facing the clutch drum...which makes no sense since chips could just pack in there/limited air flow. I turned it to the vents facing outboard, now the solid face to the clutch drum.

Chain now spins both ways no problem. Still does not seem like it should make any difference which way its mounted in regards to chain alignment/clearance but obviously something changed because no more problems. Thanks for the replies everyone.

 

[buzz sawyer]

The sprocket pulls the chain using one side of the recesses. Since you reversed it and it now turns freely, that could indicate excessive wear on the side that originally contacted the drive links. Now that it turns freely both ways, reverse it again to see if the problem returns. If it does, the sprocket is the problem.

 

[CR888]

Don't over tension your chain too, it will cause stretch issues putting chain out of pitch. Chinese chain will stretch easily, a little loose is better that a little tight. The fact it became smoother when you reversed the rim sprocket indicates wear is taking place. Wear is normal, learning how to minimise it is key. H.P is better spent cutting wood than stretching chain or wearing metal drive components.