newer chain jumps off bar???

['bert]

Recently bought a new Stihl bar for my 028 c/w new chain. Went from 16" to 18". Worked well for first 2 tanks of fuel. Went out tonight and within the first 2 cuts it jumped off the bar and destroyed about 6 of the drive links. I did check the chain tension just before heading out, seemed right. Drive gear is also in good shape. Don't think i hit anything as all the cutters and rakers are fine.

Would be interested in some thoughts of what could have caused this. Just not sure what i did wrong, I have had this saw for the better part of 10 years and have never had anything like this happen. Can chains be defective? Also is it worth trying to repair the new chain, or am i just risking wrecking a new bar to save a chain?

 

[kevin j]

is it the right gauge chain for the bar?
the burrs on sides of drivers can usually be filed off and it is fine. If there is a tight link, may be a problem, depends on how it was damaged.

Were you cutting branches or < 1 inch stuff? that snags and throws off chains if there is any side load.

Is the bar aligned with the sprocket? assuming spur not floating rim, if the bar has dirt behind it, it will be off alignment. If you loosen the cover nuts too far, dirt can get behind bar.

 

[Saw-dust]

New bar, new chain but old sprocket.

Longer chain is more picky about staying tight. After two tanks that chain started to work the slack out of it. Then the chain gets hotter on bigger cuts, it gets even more slack in it. Then you start to make another cut. You pull the throttle back, the chain goes fast but it is flying real loose. Any little anything can push that chain right off the tracks.

Old sprocket can do it too. When you cut the chain is pulled tight against the sprocket and it seems like running smooth. When you slack that chain and it is going fast, that chain goes walking all over that sprocket, side to side and forwards and backwards. New chain, new bar, new sprocket, on the business end you got a new saw.

I only use Sthil chain. They dont strech too bad but i always look at the chain when I fill up then I check again a little latter when the chain is hot. Then you know about where you are on chain being tight.

KJ is right, that little stuff will derail a chain in a heartbeat. Before I get into brush I look that chain over good.

If you got a new bar then get another chain, don't waste the bar any more, they cost too much. Sprockets are about 15 bucks for my 029 and easy to change. Chances are the clutch side is shot too and that comes with the sprocket.

good luck dude.

 

['bert]

i went out back and looked again after the post 'bout the small stuff. I was fighting with some other branches in my way last night. Dusk comes early in these parts at this time of year. What i found was a branch with saw marks on it right about where that chain came off!. Coincidence... i think not.

Drive gear is in good shape, new this spring (10 - 12 tanks of fuel old). That was part of the reason I decided it was a good time for a new bar (and the fact that i could not justify a new 361 when this and the husky 61 seem OK, well the 61 is less OK).

touched up the drive links with a file and they seem fine, runs in the bar grove smooth. Ran the saw and all seems well. Will try some cuts tomorrow to find out.

Guess i have lucky till now.

 

[Saw-dust]

i went out back and looked again after the post 'bout the small stuff. I was fighting with some other branches in my way last night. Dusk comes early in these parts at this time of year. What i found was a branch with saw marks on it right about where that chain came off!. Coincidence... i think not.

Drive gear is in good shape, new this spring (10 - 12 tanks of fuel old). That was part of the reason I decided it was a good time for a new bar (and the fact that i could not justify a new 361 when this and the husky 61 seem OK, well the 61 is less OK).

touched up the drive links with a file and they seem fine, runs in the bar grove smooth. Ran the saw and all seems well. Will try some cuts tomorrow to find out.

Guess i have lucky till now.

I think you got it figured out. I fix my buggered up chain like that too. You never know what people can or cant do is why i said get a new chain. You know how to fix it and most people I know do like that too.

Longer chain can be a little tricky to run, real tricky when they are new. but after you get the slack streached out and you should be about there, it no big deal. Just remember after a big cut that chain and bar gets hot. That is when you need to see how the chain is tight. My big saw is a 24 inch. I'll fill up. I'll think the chain is a bit too tight but I'll leave it alone. after it gets hot I'll look again. Some times I might find a half inch gap between the chain and the bottom of the bar. You never know, at least i dont anyway. You just have to keep an eye on it. Do that and you wont have much problem.

 

[kevin j]

if you need to change sprockets, rather than spend $15 for (I assume) a spur sprocket/clutch drum, convert it to rim sprocket. I think it was $26 or so for the clutch hub with spline, and a slip on rim sprocket. Then you only need to change the sprocket after that for about $6 a time, and they can be reversed every so often to get double wear. Also, on two saws recently I changed from 7 to 8 tooth sprockets to see how it worked. One didn't work out, but only cost $6 and 10 minutes to try the different ratio.

kcj

 

['bert]

Thanks for all the advice everyone. Took it out this morning and it ran just fine. Good heads up on the extra slack that will come with a longer chain. Just got back in and yeah there is alot of slack there. :roll:

So Saw-Dust, you actually start with your chain a bit tight and let it work loose?

Are these longer chains going to continue to expand - contract or will it stabilize after a bit?

Last question, do you loosen the chain off after your done? Never did with my 16" and it always seem fine, hardly ever had to adjust that one.

kcj, do you have a link to these other sockets? I am intrigued.

 

[Saw-dust]

Thanks for all the advice everyone. Took it out this morning and it ran just fine. Good heads up on the extra slack that will come with a longer chain. Just got back in and yeah there is alot of slack there. :roll:

So Saw-Dust, you actually start with your chain a bit tight and let it work loose?

Are these longer chains going to continue to expand - contract or will it stabilize after a bit?

Last question, do you loosen the chain off after your done? Never did with my 16" and it always seem fine, hardly ever had to adjust that one.

kcj, do you have a link to these other sockets? I am intrigued.

On a brand new chain I'll start abit tight cause I know it will streach. How fast they finish streaching depends what you are cutting. If you got a big log to cut it can do the whole trick after 7 - 8 cuts. With little stuff it might take all day. Don't worry though it will quit streaching out and be like running your 16" after it is done. You just have to wach them close at first. Keep you chain tool handy but once they are done streaching, they are done streaching and you are good to go.

Orgone is good chain but it will streach a bunch and go slack in a hurry when it is new. Still claims ther chain is pre-streached. It dosent seemd to slack off as bad as the other so I guess they are true on that. both cut good and run smooth. Oregone flat top chain may be a bit faster cut but that can depend on what you are into. soft wood i like Oregone, hard wood i like still but that is just me. ritht now all I have is sthil chain and I'm fine with that for everything.

Yea if the chain is hot you can get way too tight after it cools off. I have backed them off before to keep that from happening. I let a poulan saw get too tight like that one time and it cracked the crank case back by the sprocket.

Here is how I like my chain after it is streached out finaly. With a cool saw i like the chain (the black link part of the chain) to hang off the middle of the bar about 1/16 of and inch or less. I don't like it tight against the bottom bar at all. Just a wee bit loose where I can spin it by hand easy.

 

[chad3]

Same as Saw-Dust. I have a Solo with a 28 in bar and it dropped the chain a few times the first times I ran it. Make sure it is pretty tight during the first fire up of the day and you should be good. As a side, the longer the bar the harder time you will have of cutting straight when you are felling the tree. Just make sure you have the bar horizontal. Long bars are great for big wood, but a bit more checking is the norm.

 

[kevin j]

Q kcj, do you have a link to these other sockets? I am intrigued. Q


Here is an oregon link.
http://www.oregonchain.com/sprockets_spur_rims.htm

Shows the spur (fixed) sprocket and replaceable rim type. I think a conversion set is maybe $25 or so last time I priced.


Oregon makes clutches and parts for many mfrs, so many others may fit your saw. There is a small 6 spline hub, small 7 spline, and large 7 spline. Onto that hub slides various replaceable rims. I just tried a 8 tooth to replace the 7 tooth on a Dolmar 7900. Wanted to see if it could pull the increased speed on short bars. No dolmars around here, so went to stihl dealer and got it. Cheaper than changing the whole hub, plus if you change bar sizes during the day for a specific tree, or change bar and chain pitch, you just change the rim and don't get dirt in the clutch bearings.



CHAIN STRETCH
Another topic: Chains (roller drive chains, or saw cutting chains) don't STRETCH, despite the common use of that term. (They could under extreme load, but not during normal operation, and that would very shortly before failure). The pins and bushings WEAR microscopically, but it adds up. In say an 84 driver chain there are 168 pins. If each surface only wears 1/10 of one thousandths of an inch, it is still 168 x (pin + bushing surfaces) or 336 x .0001 or over .030 wear in length. That would be equivalent to moving the bar in 1/16 of an inch, so that is pretty loose. Doesn't take much wear to cause the chain to move away sideways from the bar.

So, initially, the punched or stamped surfaces are not super smooth, the high spots wear off and the bearing area increases and the wear is decreased. The tiny wear particles then cause more wear if they stay in the joints. The lighter the load and more lubrication, the better this process of breakin goes, and flushes out the micro particles. Newer saws are really stingy on oil also. I don't like dipping chains, or storing dripping chains. I either pour some in the top bar groove, or after putting on a new chain slop a little bar oil on the side of the bar near the top chain run, tilt the saw to get it to run into the links, and run it slow speed (so it doesn't sling off so much at the tip) for a few seconds. Not sure if necessary, but it must help some....


kcj

 

[BJ64]

CHAIN STRETCH
Another topic: Chains (roller drive chains, or saw cutting chains) don't STRETCH, despite the common use of that term. (They could under extreme load, but not during normal operation, and that would very shortly before failure). The pins and bushings WEAR microscopically, but it adds up. In say an 84 driver chain there are 168 pins. If each surface only wears 1/10 of one thousandths of an inch, it is still 168 x (pin + bushing surfaces) or 336 x .0001 or over .030 wear in length. That would be equivalent to moving the bar in 1/16 of an inch, so that is pretty loose. Doesn't take much wear to cause the chain to move away sideways from the bar.

So, initially, the punched or stamped surfaces are not super smooth, the high spots wear off and the bearing area increases and the wear is decreased. The tiny wear particles then cause more wear if they stay in the joints. The lighter the load and more lubrication, the better this process of breakin goes, and flushes out the micro particles. Newer saws are really stingy on oil also. I don't like dipping chains, or storing dripping chains. I either pour some in the top bar groove, or after putting on a new chain slop a little bar oil on the side of the bar near the top chain run, tilt the saw to get it to run into the links, and run it slow speed (so it doesn't sling off so much at the tip) for a few seconds. Not sure if necessary, but it must help some....


kcj

That is good stuff to know.

 

[chad3]

I'm on the opposite end of the pool. Bar oil is cheap, I'll sling a bit. To this end, I put a 460 High Output pump into my 361 (yes it can be done, if you want to know, PM me). This goes from a stingy oiler to one that if you aren't aware you will run out of oil. For hard wood (and dry on top and even more so) you want more oil so you done burn the chain and bar. Its a great add on for a pretty small price. Other saws are still pretty good but can't get past the EPA deals on oil for bars. Don't know if I want to know where these saws are going to be in the next year once the stricter laws come. However, they will still be producing they "bad" saws as they get credits for the non epa saws.
Bring on the oil, Wally World will sell bar oil for about 6 bucks a gallon and it is pretty good as a side.
Chad