Chain keeps falling off saw (stihl ms 290)

[recycledsole]

Hey guys,

I dont know whats going on with my chainsaw. Ive been cutting small trees and brush and the chain keeps falling off. I have it a little tighter than normal to try to combat it, but still happens. I put a new chain on it today (but accidently cut against a brick for a few seconds). It is falling off the tip and around the wheel part that makes it turn. its a ms290 stihl, only 7 months old. could it be the dull chain? any advice would be appreciated. thank you very much

[RopeKnight]

I would take a look at the tensioning screw may be worn/stripped.

Or the chain is worn and stretched and is also at the limit of the tensioning screw and so once the chain warms up all the tension is lost.

All I can think of. I've been there and think it is the latter.

[Gus McWilliam]

Is the bar the right size or worn?

[landrover 101]

If you didn't have the problem before the new chain then the new chain must be the problem

Compare it to your old one as you may have a 325 and 3/8 mismatch somewhere which would lead to them coming off

 

 

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[Andy Collins]

Take a look along the bar groove, make sure there are no small twigs along it, run a groove cleaner through it. Have you nipped/twisted the bar slightly, that may cause the chain to jump up and off?

[Grass hopper]

count the chain links , new and old and see if they match ? rule it out.

[normandylumberjack]

Check the drive links are not damaged or burred, do they slide through the bar groove freely? this can cause a chain to jump off.

[martwizz]

check that the nose sprocket of the bar hasn't started to split, we had a similar problem with our pole saw a few weeks ago, and that was the problem.

[spudulike]

Check the bar isnt bent - take it off and put a straight edge against it!

 

Is the oiler working OK - lack of oil can make the chain tighten and eventually come off - first sign is overheating and a brown coloured chain that is stiff.

 

Do you put a wood chock under the bar tip and push the saw downwards when tightening the chain - it pretensions it and stops the bar moving on the first cut.

 

Are you doing the bar nuts up tight enough?

 

Larger Stihls use 1.6mm gauge - are you sure your chain is correct and not wishing to teach you to suck eggs but make sure the chain is the right pitch - 0.325 and 3/8" are the most common. Make sure you have the right one.....I have seen a 3/8th on a 0.325 sprocket before:001_rolleyes:

[Stubby]

If your bar rails are worn down you can get a situation where the drive tangs don't sit in the groove correctly . If you can rock the chain from side to side ( a significant amount ) after tensioning the the bar at best needs the rail dressing and worst its shot .