Sthil 441 Chain Tensioner Breaking

[Choposaurus]

Hi everyone

So I'm a first time poster long time reader and basically what it is, is an issue with my Sthil Ms441 where the chain tension keeps breaking. I'll give you a run down of the history and current setup. I bought the saw second hand about a year ago, used it a few times but always had the same problem. The saw runs and starts fine, as far asi can tell the chain lubricates and the saw itself runs sweet as a nut. The problem is, afterabout 10-15 minutes of use the chain tensioner literally shatters and i can't explain why.

At first i put it down to the fact that the part might be old, so i bought a new one.. cheap one off eBay and again within 10 minutes the adjuster plate broke. Tried again noticing that the Thrust Pad (part at the end of the housing) was missing. Got another cheap one, this time the screw bent but that was only after about 5 minutes. So thought cheap ones are the problem. So went to local Sthil guy and bought the whole tensioning set up from the dealer. But again, within about 20-30 minutes of use the system broke. Actualy just disintigrated...

I beleive the issue now to be some where else other than the tensioner and i'm struggeling to identify where the actual issue lies... Has anyone else got any ideas or ever come across a problem like this. I'm finding it to be a real head scratcher?

25"Bar and chain on the saw and ive counted the drive links and the chain is the correct size

 

I've attached a few pics to show where the issues lie and if you guys need any more info just let me know.

 

Thanks in advance ?

Ell

[Stubby]

Odd . I don't have a Stihl so cant help . Never had this on any of my saws . ( had the odd one break but not repeatedly like this ) . Would be interested in the outcome though . Hope you get it sorted . Must be frustrating .

[billpierce]

What bar are you using? Is it definitely the correct one for the bar stud size?

[Stubby]

17 minutes ago, billpierce said:

What bar are you using? Is it definitely the correct one for the bar stud size?

Or the tensioner  stud . Does it go all the way into the bar and not hang up on the taper ?

[Mark_Skyland]

Those bar studs look different, can you check as they should be the same?

 

Never had that issue before so I'm thinking the bar is moving up and down causing the screw to snap.

 

 

[lurkalot]

Obviously the bar is moving when using the saw, otherwise the adjuster wouldn't break.  The tensioner only holds the chain to the required tension until you do the bar nuts up, after that it should be doing nothing while your using the saw.   Are the studs seated properly, or does the shoulder on one or both the studs protrude too far, thus not letting the side plate clamp the bar?

 

Bottom line is the bar isn't being clamped in place properly.  That's my theory.

[Dan Maynard]

Have to agree it's not clamping. Another idea - one of the studs on my secondhand saw had been stretched be overtightening, as the threads are now a bit too far apart on that part the nut goes tight before pulling down onto the bar so I have a couple of washers behind it.
One other thought, is the sprocket definitely ok as maybe if that sticks then the chain would pull in on the bar? Can you borrow or swap the bar to test?

[ESS]

From memory there is a backing plate on these saws that you would have to remove to change the tensioner.Pretty sure that on some Stihls you had to remove the bar studs to remove the backing plate. If that is the case have you made sure that both studs have been fully tightened into the crankcase when replacing, if not one of them could be undoing itself a little when you slacken the bar nuts and the bar not seating properly .

[Choposaurus]

Thanks for your replies everyone, I do agree that it does seem that the bar is resting on the tension pin rather than being held in place by the by the stud screws. The bar itself is the correct bar for the saw ( Sthil 3003000523) i know the saw had previously had some work done on it when it was serviced as i was provided with the paper work. I'll have a proper go at it tomorrow in the workshop and see what i can find.

Thanks again for the help and i'll keep you posted ?

[billpierce]

Thanks for your replies everyone, I do agree that it does seem that the bar is resting on the tension pin rather than being held in place by the by the stud screws. The bar itself is the correct bar for the saw ( Sthil 3003000523) i know the saw had previously had some work done on it when it was serviced as i was provided with the paper work. I'll have a proper go at it tomorrow in the workshop and see what i can find.
Thanks again for the help and i'll keep you posted [emoji106]

Hope you get sorted. As said there should be a plate that screws over the tensioner. I'd fit the bat and look in under and from the front and check the cover plate is pulling in real tight.