What's wrong with my bar?

[Daniël Bos]

I have a slightly puzzelling issue with my 550xp.

Started work this morning and within a second of starting to cut it threw the chain off, it did not break, just came off. It was tight when I started and when I put it back on it still was tight? How on earth did it come off?

 

The 550 has the adjuster built into the clutch cover, so taking off the cover slackens the chain. Don't know if that could have ought to do with it?

 

The when I got home I wanted to cut up some off the wood I took home, put a new chain on the saw, the first since I've had the saw. I flipped the bar, put it on, nice and smooth. Then put the cover back, all smooth until I fired it up and the chain was nearly solid!

Took it off, had a look, the chain moves freely through the bar, the drum and sprocket seem fine, no obvious obstructions.The chain-brake moves as it should, and releases fully.

 

Put it back on, same thing! All is smooth until I tighten the bar nuts.

 

Put it back on with the bar the other way up and all was as it should be. The bar was new with the saw and has not seen it's first chain out yet.

 

 

 

Any clues?

[Treecreeper1961]

I have a slightly puzzelling issue with my 550xp.

Started work this morning and within a second of starting to cut it threw the chain off, it did not break, just came off. It was tight when I started and when I put it back on it still was tight? How on earth did it come off?

 

The 550 has the adjuster built into the clutch cover, so taking off the cover slackens the chain. Don't know if that could have ought to do with it?

 

The when I got home I wanted to cut up some off the wood I took home, put a new chain on the saw, the first since I've had the saw. I flipped the bar, put it on, nice and smooth. Then put the cover back, all smooth until I fired it up and the chain was nearly solid!

Took it off, had a look, the chain moves freely through the bar, the drum and sprocket seem fine, no obvious obstructions.The chain-brake moves as it should, and releases fully.

 

Put it back on, same thing! All is smooth until I tighten the bar nuts.

 

Put it back on with the bar the other way up and all was as it should be. The bar was new with the saw and has not seen it's first chain out yet.

 

 

 

Any clues?

 

I have had saws that have puzzled me when tensioning the chain. Sometimes tightening the nuts seems to tighten the chain too. Try tensioning so it is a little too slack, with the nuts just slackened off enough, rotate the chain several times, tighten the nuts up and see how it is.

 

Don't know how it could be different with the bar flipped??

[Stubby]

I have a 560 so have the same tensioner design . All I can think is the taper on the peg that engages with the hole in the bar is not fully home when you do the adjustment so when you finally tighten the bar nuts the taper pushes in deeper pushing the bar forward just enough to tighten the chain too much . To overcome this ( if it is this ) you need to have the cover almost tightened , just loose enough to make adjustment but only just .

[Tom D]

The "tang" on the adjuster that fits into the hole in the bar will be tapered, if its not fully seated home it will pull tighter as the bar nuts are tightened. maybe you had the chain off the sprocket when it threw it?

 

Like others have said fit bar and chain properly and loosely fit side cover then check the chain is rotating freely then tighten the chain.

 

One final thought, perhaps some of the drive links are damaged, if they have become burred by the chain being thrown they will not sit properly in the rails in the bar. Take a flat file to the burrs.

[spudulike]

I have a 560 so have the same tensioner design . All I can think is the taper on the peg that engages with the hole in the bar is not fully home when you do the adjustment so when you finally tighten the bar nuts the taper pushes in deeper pushing the bar forward just enough to tighten the chain too much . To overcome this ( if it is this ) you need to have the cover almost tightened , just loose enough to make adjustment but only just .

 

Beat me to it:thumbup:

 

I usually do the bar nuts up tight enough that you an just move the bar tip up and down and then adjust - I pull the chain off the top rail on doing up the bar nuts so it pulls the bar tip upwards on tightening - this stops the bar doing this in use and tightening up after a few cuts.

[normandylumberjack]

I had a similar thing happen with a stihl, it was a damaged drive link on a new chain, like tom d suggests.

[Daniël Bos]

Thank you, thank you.

It was indeed the way the conical peg moves as it's tightened, I've not had a saw with an "outboard" tensioner before.

[ecodao]

My Big Echo is a mare for this , i do exactly what Spud has suggested ,

tighten it up nearly all the way , then pinch up the chain so the nose of the bar is as far up as it can go , then adjust and tighten fully.

 

although every so often nothing seems to work for about 20 mins of fiddling !! :-)

[Pedroski]

Lifting the tip of the bar when adjusting and rightening the nuts is also something that the Makita manual instructs the owner to do. Is this in Stihl and Husky manuals as well?