chain adjustment

[lostone]

I am not sure exactly what the problem is, I put a new chain and 14" bar with a 3/8" pitch .050 gauge (had same setup before but with a longer 16" bar and worked fine but previous bar is just to much for the little sucker) The sprocket is an oregon spur with new bearings. When I start to adjust the chain I bring it up so it just starts to touch the bottom of the bar then pull down on bottom of chain to make sure it comes back to bar (holding bar pulled up at all times), everything feels good at that point then when lock the bar into place and pull the chain to feel the drag it will either loosen up at the bottom or tighten up to to much drag on the bar. If i adjust it so that there isnt to much drag on the bar when I pull the chain around by hand to check the drag there are times that the chain will be sagging and the bottom away from the bar a heavy 1/16" . I have checked the groove and cannot find any debris that the chain would be picking up to cause it to tighten and loosen as it goes around the sprocket or sprocket tip the links on the chain all look to be the same where it goes around the sprocket and groove. At first i thought a misalligned spocket but then I never had this problem before with the other bar. Then I checked the bar tip and it SEEMS to be the same when spinning it by hand and wacthing for it to be out of round. When I bring the chain to a happy medium then run the saw (with plenty of oil on it and not cutting for say 15 seconds) you can cook breakfast on the bar and chain it is so darn hot. Just has me puzzled, was wondering if anyone else has run into this same delima? should I dump the new bar and chain and replace? Sorry for going on so long but wanted to give as much info as I could.

 

[cbfarmall]

Not sure if you mentioned it, but did you change the sprocket? If it is out of round you would certainly be seeing the problem you describe. If the spur teeth are grooved, you will wear out your chain in no time.

Chris B.

 

[lostone]

the spur is fairly new, no wear on it. I don't use the saw much. All I can think is maybe I just didn't pay enough attention to the previous bar and chain to see the sag in it (this is a windsor bar the previous was a oregon bar) I would like to get a sprocket for it that is the power mate but I don't know if they make one for the little saw (pm 6) I currently have a oregon spur part # 29888 on the saw now, but I can't find a conversion chart on oregons site to find out if I could go with a power mate sprocket. thanks for the fast reply.

 

[tony marks]

u got what i call a phatom problem...
sooner or later u probably will find the problem.. but was it me,, id start over again.. these various new parts ,that are suppose to be matches, are in many cases,, off just enuff to ruin your saw.. jmo

 

[mlk]

There is a difference between 3/8" and 3/8" lp (low profile) chain. Do the drivers on the two chains look the same? I think if there is a mismatch between sprocket, chain and bar pitches, with one or more being 3/8 lp and the others being regular 3/8, you could get the problem you describe.

The only time I have experienced what you describe is with a HT75 pole saw with 12" bar. The situation resolved after I cleaned a bunch of oily sawdust out from around the sprocket and sprocket cover.

 

[glens]

The difference between 3/8 and 3/8LP is above the rivets, not between them.&nbsp; If it were a chain <i>pitch</i> issue there would be abnormal difficulty pulling the chain.

If it were a problem that manifested itself every 6 or 7 drivers (whatever the tooth count on your sprocket is) then I'd suspect an eccentric bore in the sprocket (like maybe from idling a tank or two through the saw with the chain too tight and a bad sprocket bearing?).&nbsp; For such a case I'd opt to have the chain tension be right when at it's tightest point; the clutch drum will center on the clutch when it engages and the tension should remain steady in operation.&nbsp; If the spur itself isn't eccentric...

Something else to look for would be a ham-fisted splice in the chain.&nbsp; Look for an excessively tight joint which doesn't allow the chain to straighten fully when along the bar.&nbsp; Such a critter will suddenly allow the tension to drop while it's at the spur (and maybe nose).

Some other basic things to look at would be to ensure the bar mount nuts are somewhat snug while adjusting tension, and to have the final movement of the bar be outward, so all the slack in the adjuster is taken up.&nbsp; (if you get the chain too tight, loosen it too much and bring it tight again)

If the problem manifests itself without ever turning the engine over then it's probably not a bent crank.

Glen

 

[lostone]

Thanks for all the tips, I will be able to check the saw out tomorrow night and see if one of the tips will help. I still have the oregon bar its like new also I will put it back on and see if the problem existed with it also and that I just didn't notice it. Again thanks for all the help. Will post what turns out.

 

[Crofter]

Lostone;

Had some similar problems with a new bar, and the culprit was paint in the groove plus a bit of a pinch at the heel of the bar. It really was heating up until I cleaned it out. A seven or eight cornered wheel does have slight lumps. An out of round sprocket is quite common even new but the lumps that gives are much further apart.

Frank