MS880 keeps breaking off chain tensioner stud

[mikereiche]

My MS880 keeps breaking off the stud on the chain tensioner - see image. These are genuine Stihl parts, not knock-offs. Any ideas? I've tried spot welding the stud in hole, but the weld weakens the plate and it breaks

 

[northmanlogging]

sounds like user error, only adjust chain tension with the bolts loose, then tighten them
really shouldn't be a lot of stress on the tensioner pawl once the bar is tight.
The other thing it could be, is a worn or loose bar stud, allowing the bar to move far from its normal position, which would be extreme.

 

[singinwoodwackr]

Rakers filed down too far?
Bar nuts loose?

 

[rogue60]

Agreed user error do the bar nuts up properly.

 

[mbrick]

Tighten the bar nuts then back it off a touch?

 

[sawfan123]

Hold the bar up when tightening. Way way too much weight, between a .404 chain and bar, on the stud.
Basically lift the weight off the stud.

 

[trains]

My MS880 keeps breaking off the stud on the chain tensioner - see image. These are genuine Stihl parts, not knock-offs. Any ideas? I've tried spot welding the stud in hole, but the weld weakens the plate and it breaksView attachment 1109366

What length bar are you running ?

 

[Dennisthemenace]

User error I'd reckon. Were you boring in and getting kick backs?
I've damaged my Husky 394 front tensioner bore cutting but never a 084 or 088

 

[HarleyT]

Put up a pic of the bar, chain, and sprocket.

 

[ZeroJunk]

Hold the bar up when tightening. Way way too much weight, between a .404 chain and bar, on the stud.
Basically lift the weight off the stud.

Or, you can just push the top handle forward. Little easier maybe.

 

[rtrsam]

I've run saws without the tensioner on it at all, the bar nuts hold the bar in place. Especially on a longer saw, 088 with a 72" or 84" bar, no tensioner on it.

Anything longer than 36" I wouldn't even bother trying to get the chain on the bar when assembling, just bend the bar sideways until you can pop the chain over the tip, then loosen the nuts a little, jerk it tight (helps if you have a vice or two guys) and tighten the bar nuts

 

[sawfan123]

I've run saws without the tensioner on it at all, the bar nuts hold the bar in place. Especially on a longer saw, 088 with a 72" or 84" bar, no tensioner on it.

Anything longer than 36" I wouldn't even bother trying to get the chain on the bar when assembling, just bend the bar sideways until you can pop the chain over the tip, then loosen the nuts a little, jerk it tight (helps if you have a vice or two guys) and tighten the bar nuts

This probably make the most sense. Cant break if it isn’t there. I dont think that tensioner could push a 36”
.404 bar. It would snap for sure.

 

[Dennisthemenace]

I've run saws without the tensioner on it at all, the bar nuts hold the bar in place. Especially on a longer saw, 088 with a 72" or 84" bar, no tensioner on it.

Anything longer than 36" I wouldn't even bother trying to get the chain on the bar when assembling, just bend the bar sideways until you can pop the chain over the tip, then loosen the nuts a little, jerk it tight (helps if you have a vice or two guys) and tighten the bar nuts

Yes, there is something in what you say

 

[rogue60]

One problem with guys that are to tentative doing up bar nuts (apart from snapping tensioners) is the clutch cover bar pad wears and will no longer be flat.
Take a straight edge and see how worn the clutch cover bar pad is. If worn take a flat file and dress it flat.

 

[mikereiche]

Mostly milling with a 41" bar.
Thanks for all the information and suggestions. Probably the bar nuts not tight enough. The nuts sometimes come loose while sawing - does anyone use a lock washer?

> Tighten the bar nuts then back it off a touch?

> I've run saws without the tensioner on it at all, the bar nuts hold the bar in place.

These are good ideas.

> Rakers filed down too far?

Also very likely.

 

[singinwoodwackr]

Mostly milling with a 41" bar.
Thanks for all the information and suggestions. Probably the bar nuts not tight enough. The nuts sometimes come loose while sawing - does anyone use a lock washer?

> Tighten the bar nuts then back it off a touch?

> I've run saws without the tensioner on it at all, the bar nuts hold the bar in place.

These are good ideas.

> Rakers filed down too far?

Also very likely.

Don't back off on the nuts

 

[Aknutter]

Maybe get a new set of bar nuts and or change out the bar studs.

 

[mikereiche]

Don't back off on the nuts

I understood him to mean "backoff the tensioner after the nuts were tightened, so that if the bar did move, it wouldn't break the tensioner"

 

[Skeena2]

Did the same thing when getting familiar with my 881. User error caused the issue. I was able to silver solder the tensioner back together in addition to picking up a spare new one.

 

[J D]

The nuts sometimes come loose while sawing - does anyone use a lock washer?

The nuts should never come loose... need to put a bit more oomph into tightening em. Don't use lock washers, they'll chew through the cover. If you've got a torque wrench use that to do them up to spec & then loosen/ re-tighten with your normal tool... should give you a good idea where it should be at