Chainsaws

Keith,

Yes - I have seen it on a model 460, which in fact was my neighbors, and he knew I worked on Husqvarna chainsaws, unfortunately I did not have the chainsaw long enough to do a thorogh diagnostics of what was causing the problem, because when I told him he needed a new bar and chain for starters, he took the saw back. But what I did see was that every drive link was twisted and the chain would not fit back into the bar. I suspected that possibly he had the incorrect gauge bar for the chain gauge like maybe a .058 gauge bar with an .050 gauge chain. I also asked him what he was doing at the time when this happened, but he did not give me a direct answer, so my second thought was that he had pinched the bar in a tree, which obviously would close up the bar groove making it a different gauge and not fitting correctly.

Anyhow, I gave him the chainsaw back before I could completely solve the problem, which was frustrating for me, and he may have just gone out and bought a new bar and chain on his own, and never told me If this solved his problem.

I would recommend checking everything from the beginning:

1. First check the pitch of the drive sprocket, the pitch should be marked on the drum, or there will be a part number, and then you can look the part number up and verify if its a .325 pitch or 3/8 pitch, Do Not Guess, make sure. ( I recently worked on a Model 435 that had a .325 pitch drive sprocket with a 3/8 pitch chain on a .325 pitch bar) This will not work and could cause the chain to come off the bar, and depending on how the chain comes off could twist the chain links.

2. Second check that the bar pitch is the same as the sprocket, this pitch is important because, the nose of the bar may have a sprocket in the nose, this sprocket is similar to a gear, and will have a pitch to it. If you try to put a 3/8 pitch chain around a .325 pitch nose sprocket, It will kind of fit but if you look closely at the bar nose you will see the chain is pushed out from the nose and just being supported by the sprocket, this is wrong and another way the chain could come off the bar.

3. Third check that the pitch of the chain matches the pitch of the bar, and is the same as the pitch of the drive sprocket. Everything must match or the chain will have another good reason to come off the bar. Also the chain gauge (ie. .050) must match the gauge of the bar groove (ie. 050).

4. Finally I would check the condition of the bar and chain. Insure the bar is flat, and straight, and there are no bends or pinched groove spots in the bar. Make sure all of the chain links move freely and independant of each other, I assume your buying new chains so this should not be a problem, but I always do this as part of my checks because I get alot of abused and mis-used chainsaws to test and fix.

When you Install the chain on the bar make sure the tension is correct, not too tight and not too loose. I always pull on the chain (with a glove on my hand) for at least a couple travels of the chain to go completely around the bar, making sure the chain pulls easily and there are no hiccups or bumps in the road while your pulling on it, If there are then stop and investigate what is wrong. A bad drive sprocket witll cause this problem.

5. I almost forgot but its very important that everything is always clean and kept clean, and very well lubricated, a piece of wood chip stuck in a bar groove can make the chain jump too. The Drive sprocket bearing, and nose sprocket, needs to be periodically cleaned and re-lubricated, the chain needs to move freely around the bar with an un-interrupted motion, or No hiccups.

Maybe one last thing, but I mention this because you said it was a new chainsaw. I remember one individual was running his chainsaw with a piece of packing material which was orginally installed on the bar bolt, (Looks like a styrafoam washer), It was suppose to be removed when the bar was installed. However the individual put the bar ontop of the styrafoam washer, and clamped the brake cover on with the bar nut.( Note: How that chainsaw ran in that condition is beyond me, I think until the chain came off!) So as impossible as it sounds, make sure their is not a styrafoam packing washer left under your bar. 

I can't think of too many other possibilities, in answer to your question, and sorry to be so wordy.

I hope this helps, and please let me know what you discover.

Karla

PS. I am Not a Husqvarna Representative or a Repair Service, just an experimental chainsaw person