Had this problem a couple times now. The chain pops off as I am cutting. I put the chain back on, it turns and then after a bit more cutting it pops off. A while ago I notice my chain had burs in the drive lugs. Replaced the chain and was good for a while. After my last two times putting chain back on I noticed it won’t spin manually. And when I fire it up now it doesn’t spin at all. My nose sprocket doesn’t spin, and chain isn’t very easy to get back in the bar grooves. FWIW, it’s my original Husky bar. 550xp. if I need a new bar, .325 and .058 is standard right? Thanks for any advice.
make sure the sprocket it free on bar, and file it down, clean out the rails.take burrs off the sides after.
file top and bottom of bar back to square if the nose sprocket is free. your bar may need squeezed if you ran it too long. dont know if this makes sense.
OK, thanks. I'll check the drive links tomorrow. I use the scwrench to tighten the chain. I tighten to the point where I can pull it fairly easily from the bar. Can't really explain, but I don't tighten super tight. what's a spur or rim sprocket? FYI, last time I had this problem, I did a thorough cleaning. Cleaned out the bar rail. Etc.
Also on the bar toward the mounting slot there should be some writing telling you if the bar is .325 and .058. I would check it to make sure that is what you have. If the drive teeth are chewed up then that would make it hard to go through the bar slot smoothly and freely.
Remove the bar & see if the nose sprocket turns freely. Look at the drive sprocket on the saw for damage to the teeth/wear. Make certain the chain is the correct pitch & gauge for the bar. If all these are good, sight down the bar groove & look for a bend, uneven rails or other damage. If the chain drivers are damaged most likely is a worn/damaged drive sprocket, or mismatched chain. Let us know.
Chain coming off is usually from a couple of reasons First is chain adjustment the chain should roll by hand with a slight resistance it should be tight against bar that it will not droop away from bottom of the bar second is a oiling problem that is causing the chain to run hot and stretch when you throw the chain off at high rpm the chain is caught by the chain catcher on saw and the drive links hammer against the drive sproket which deforms them if you put them back into bar it causes wear on bar,excessive tension on chain and friction which causes wear and heat you must have had to force chain back into the bar to make it not spin at all if your nose sproket does not spin free I suspect that the saw has a oiler problem and or you have damaged the sproket once you have damaged the drive links on a chain you either have to file or grind them back to shape or toss the chain hope this helps JB
So before you make the final tighten with the bar nuts, lift up on the bar nose. This usually makes the chain a little looser. Hold it in that position when you tighten the nuts. Imagine when you are pushing the saw while cutting, if the nuts aren't tight enough, the bar can slide to this position and make the chain that little bit looser. A loose chain will derail more frequent than a properly tensioned one. Try making it a little tighter than you do. When I am processing apple tree's, I have to do that very thing to prevent chains from coming off. The very small shoots have a way of assisting the chain in exiting the bar.
Easy fix. Buy a new chain, bar and rim sprocket. Once you have those you can look at all your old stuff and see if it’s worth fixing. Do you have a Stihl shop near you that will custom cut chains! Biggest improvement on my 550’s was switching from Husky/Oregon chain to Stihl. They cut a wider kerf. The combo of high power and speed matched with a thin kerf chain like husky has is a bit of a problem. They just can’t clear chips fast enough. The chips bind under the chain and sometimes inside the nose sprocket. Switch to a Stihl chain and those problems all but disappear, along with stretching.
Ok. An update and some pics 1) looks like I have a #20 Oregon chain, which is .325 pitch and .050 gauge. That's what it says on my bar 2) I was able to turn the nose sprocket 3) Based on the pics...looks like the drive sprocket is ok. At least I can't see any visible damage. However, the bar has a bit of burring near the nos sprocket that I could file down. Finally, the chain drive links have a few spots of burring, or similar damage. Not sure if it's clear from the picture. BTW thanks for all the advice and tips already provided.
if you want to go through the effort either a dremel type tool or a hand file to clean off burrs on drive links. at the nose of your bar is a small hole on both side that is for greasing the nose sprocket. use one of the giant pen like contraptions for that job ( not expensive) i can't tell from the picture how worn the drive sprocket might be. I know my rim sprockets are not all the expensive either.
If your tossing a chain while cutting its gotta mean that your not getting it hooked up inside the rim sprocket. I like to install chain, install side cover and snug the nuts slightly, then back off the nuts a bit. Then roll chain forward and backward awhile. If it’s not properly engaged in the rim sprocket you’ll find out soon enough. Then tighten chain and nuts. If it’s just stretching from being new you have to retighten often. Oregon is made of rubber You can throw a loose chain. Usually while limbing is my experience. Chain looks new. Usually have to tighten after half a tank, sometimes less. I recommend Stihl chains.
I’ll bet it’s your drive sprocket. As it wears, your chain is able to sit deeper in the sprocket than the original groove intended, especially with the added tension created when the chain is running. I had this problem last year. I would tighten my chain, and go to run the saw, and the chain would pop off. Once you feel the chain has the appropriate amount of tension, manually turn the chain with your hand. It may become loose without even turning the saw on. If so, easy repair, and the problem was solved. You’ll have to let us know what you find out.
Sorry for the lack of response...got busy with work and other stuff. Anyhow, I took the old chain off. Got the bar tip sprocket spinning. Put the new chain on. And it runs smooth like butter. Didn't run it too long, as I am waiting to get some bar greaser. I believe the issue was the sprocket, as it wasn't spinning until I gave it some nudging. BTW, new chain is actually my factory Husqvarna chain that I had taken in for sharpening (got lazy).
