Odd rail pinch issue.

[Adamam]

Possibly stupid issue/question.

 

To cut a long story short, when I tighten the clutch cover FULLY, the bar/rail is pinched and the chain doesn't want to move.

 

This happens on two bars, one of which has never been used on this saw before today. I think therefore the issue isn't the bar(s).

 

Saw: Dolmar ps6000i.

 

Chain: 3/8 pitch chain.

 

Mounting codes on the bars are 17" B083 and 15" K095. The 15" one should be 153, but they are the same mount really (if anything the 153 mount would be more likely to pinch as it has a narrower 'tail'), and anyway it happens with both bars...

 

The pinching occurs directly above the oiler hole where I guess movement is most possible because of the lack of metal/oil duct.

 

I am baffled.

 

[Stubby]

TDC might shed some light on this .....

[wisecobandit]

You haven't got a missing metal shield or chain buffer from the cover have you?

[Adamam]

Nothing missing as far as I can see. I have 2 almost identical saws so it's pretty easy to check...

 

The only think I haven't tried is changing the sprocket, but I can't really see what difference that would make. I'm 99.9% sure the chain is being pinched.

[wisecobandit]

Try swapping the covers over and trying the bars on the other saw see if they bind on that one.

[slim reaper]

Any help? http://s30387.gridserver.com/partsDiagrams/Dolmar%20PS-6000i%20and%20PS-6800i.pdf

[Adamam]

For reference purposes!

 

I've now tried 3 bars, all of the correct mount and all 'pinch' when the clutch cover (tried two clutch covers, same behaviour) is tightened. Different chains with each bar.

 

All parts are present and correct.

 

The pinch point is directly above the oiler-hole and can be tested by trying to pull the chain away from the bar at that point (you can't because it is pinched!).

 

Solution;

 

Changed rim sprocket, but not to a new one (don't have one to hand). The newly fitted one is slightly older than the removed one.

 

Removed and cleaned/scrapped the metal shields on the clutch cover and crank case.

 

Took a fine metal file and filed/checked for irregularities on the flat clamp-faces that holed the bar.

 

Filed gently across the bar where it is clamped to check for flatness/true.

 

I don't know what fixed it as none of the above showed any obvious problems, but now it runs absolutely fine.

 

Seems unlikely to have been the sprocket though IMO, so probably a 'bump' or some gunk trapped somewhere in the 'clamp-face' causing uneven pressure on the bar?

 

Really, really annoying problem!!

 

Edited May 3, 2014 by Adamam