Randomly changing chain tension

[asgeist]

I'm having a problem on my Husky 345 that just started today,
and has me puzzled. The chain tension changes randomly from
too tight to too loose. If I adjust it, the adjustment lasts only
moments. If I tighten a loose chain, after clamping down the
nuts and starting to cut, it quickly becomes so tight that the chain
binds, and won't turn. If I loosen a tight chain, it quickly becomes
so loose that I fear the saw will throw the chain.

In experimenting, I've found that I can cause the tension to
switch from tight to loose and back again just driving the chain
by hand, even with the entire saw, bar, and chain fully cooled.
But it's not happening once per chain revolution, or anything so
simple. It's truely random.

Please help. I have to finish cutting up a tree tomorrow that
was downed by recent storms.

Thanks in advance,

A Geist
[email protected]
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[bandmiller]

Sounds like a worn drive sprocket,when chain is in worn section ,loose, when it climbs out tight----Frank

 

[ricksvar]

and if you have recently put on a new chain check alignment of bar with side plate and powerhead and chain adjustment nipple.
Everything sould be perfectly aligned/seated.

Rick

 

[sedanman]

Don't rule out the chain. A few damaged drive links can do this too, This would be most evident as the links tried to ride over the nose sproket. For that matter the nose sprocket could be wiped out. Take the bar/chain of the saw and see how the chain rolls though the rails and tip. This could be as simple as a new bar or chain or both.

 

[Crofter]

Also make sure the bottom of the bar groove is thoroughly cleaned out. Is your chain being well lubed?

Frank

 

[tony marks]

its my guess that u dont use u saw that much and have a new chain on that thinks u have gone crazy,,, as u expecting it to really do some work..
i get this impression from the work u are doing..chain stretch is an natural process.. my new barbed wire 28 is got an bad case of that,, as its got new chain..
funny thing ,,its always tite again,, after it cools.. some do this,, some dont,,which im sure has a logical reason,, but i cant figure the difference between the ones that need tightening,, and the saws that stay loose,, after they cool. somebody here knows but not me. good luck ..

 

[Oregon_Rob]

Are you running the correct pitch chain for the sprocket?

 

[asgeist]

Thanks for all the replies. Nonetheless, I didn't see a clear
winning answer, and plan to take it to the shop today. I was
finally able to find a fair "happy medium" setting that let me
finish the weekend job without throwing a chain, something this
saw has been somewhat notorious for in the past.

To answer some of your questions:

No, it was not a new chain.

No, it was not related to heat, as even with the saw completely cooled down (i.e. hours after running), I could toggle the tension between too tight and too loose just by driving the chain with my hands.

No, it's not quite oiling the chain right either. It's using too little bar oil. I'll also have the shop clean that up. I hope the bar isn't ruined. I did clean everything out, including the bar grooves, in hopes that would fix the problem. It did not.

I haven't done enough of my own work on a chainsaw to know what to look for in terms of alignment.

I do not use the saw a lot, but having gone through a few chains, I know about the issues of having a new chain on. I actually threw a brand new chain once because it got loose enough within the first tank of gas.

Again, thanks for your help. When I get the report from the shop I'll post it so those who are interested can learn from my misfortune.

A Geist
[email protected]
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[Dennis]

Try checking your chain tensioner bolt...it may be bent, stripped or broken......

 

[Gypo Logger]

In addition to what Dennis said, I think its the sprocket as bandmiller noted. When the sprocket gets worn it throws everything out of pitch causing the chain to shrink, then when you use it, it stretches. This is also compounded by lack of lube.
John

 

[Fish]

You need a new sprocket AND a new chain.

If you just replace the sprocket, your old stretched chain will
tear it up in a short time.
Take your old chain in and compare the bottom drive tangs
to a new one and you will likely see the difference.

Or it be just because you have an orange Poulan, and they all
do that.

 

[Tony Snyder]

1. I hope you are not trying to retension your chain while it is hot. If you do it will get too tight when cold.

2. Uneven or no chain oiling often produces difficulties of your type. Make sure you have some oil left in the tank when your gas runs out. Make sure your oil feed hole in the bar is kept open.

3. Forcing a dull chain to cut will cause heating of the bar a chain, it expands/chain lengthens and fools you into thinking you have some other kind of a problem. Dull chain will also pull powder instead of chips which plugs up the oil feed hole sooner.

--------------

I had guy come in with a new (purchased from afar) Husky 350 a few days ago. Chain dull as heck, bar burned, air filter totally plugged, and bar nose nearly gone. He said "I don't understand why I am having problems. That saw only has about 5 hours on it". Ya, (5 hours by a novice cutter without even a chain touchup.) The saw was covered with very fine powder.

He left happy, and wiser.

 

[ricksvar]

Checking alignment after you have taken a bar off to put on a different chain is very basic procedure.Always turn the saw up and take a quick look at the bar,side plate and powerhead to be sure everything is fitted together properly.

For example,if the nipple on the chain adjustment screw is not seated properly with the hole in the bar and you tighten the side plate nuts you could bend your chain adjustment screw/bolt as Dennis noted above.

I'am not saying this caused the problem you're having,just could.
Please let us know what the shop did to fix your saw.

Rick

 

[tony marks]

hey fish.. good to hear from u..thats what we need u know.. to h--- with that instigator crap. u da man

 

[Dennis]

Originally posted by RockyJSquirrel


Is anybody else dismayed by the wide range of replies for this basic question? I'm surprised nobody recommended he rebuild the carb!

There are a wide range of problems that could cause this...without actually seeing the saw first hand, its anyone's guess.

 

[stihltech]

tension

OK, lets add one more. How are the crank bearings? When the cage goes bad, the balls all go to one side, which would make it tighten and loose.

No, I don't think a carb kit will repair the problem

 

[WRW]

Since the problem can be duplicated moving the chain by hand, mounting the bar without the cover should make it easier to see the true nature of the problem...even if it were the bearings.

Wouldn't help much if it was carb related, though.

 

[Fish]

It is widely know that the use of synthetic oil mix can cause this
as well.


Put on a new chain and sprocket and be done with it.
Call me crazy, or at least realistic.

 

[ricksvar]

Asgeist,

Several members took time to respond to your post concerning what they thought the problem might be.Has your saw been repaired and what was the problem?

Rick

 

[Lewis Brander]

Sprocket, Chain and Bar Costs:

OK, I have a Homelite, model 600 D. saw. It has the old 9/16 pitch, .063 gauge, chipper chain and a 19", .063 gauge bevertail bar on it, that originally came on the saw. I inquired about prices to upgrade the saw with a new 3/8 pitch sprocket and drum. 3/8 pitch. .050 gauge round ground chain and last a 24", .050 gauge, roller nose bar. The prices I was quoted are. Sprocket, $28.00, Chain, $25.00 and Bar, $55.00. Does this sound abour right, or are these good prices. Just wanted to hear your comments. The email I received said the sprocket was a replacement sprocket for the saw, the chain was Oregon and no mention of what the bar was, Oregon, Homelite, etc. So what do you think? Thanks. Lewis.