MS260 broken mounting hole for chain brake

[freeasaburt]

A friend of mine recently bought a well used MS260. We've been working on our chainsaws together every now and then, so we took it apart to inspect/clean.

Turns out the hole for a bolt (right word? maybe not, it's not threaded) that holds a part of the chain brake mechanism is damaged, a part of the 'wall' has broken off.

The bolt/stud/rod/whatever the right name is (sorry, not a native speaker) holds part number 1121 160 5000 in place , which is number 7 on this page from the ipl:




I took a picture:




He mentioned he heard a rattling sound when he ran the saw first time. Turns out that the bolt that was in that broken hole has no groove for a c-clip and was completely loose, and hitting the exhaust.
Possibly it was a replacement, and maybe even the cause of the failure...?

We've been discussing how we might fix this, maybe experimenting (would be a first time) with jbweld or grinding down what's left to have a bigger flat surface to be able to tighten down a threaded rod or a bolt with a low profile head (for the exhaust side).

Does anybody have some advice here? Thx in advance.

 

[alexcagle]

Only a machinist could make a good repair on that. But the cost is prohibitive. Replace the crankcase. Don't use a hammer though lol .....

 

[alexcagle]

It's magnesium. No space. Safety critical item.

 

[thompsoncustom]

run it without the chain brake, I took mine off my 026 on purpose. chain brakes are like safeties on a gun they are good but also not needed just treat it as it's always loaded.

 

[freeasaburt]

Not exactly the replies I was hoping for, but it is what it is. Thanks for the feedback!
Might be a good idea to look for a parts saw, but they aren't too easy to find around here, in my experience.

 

[Oletrapper]

A friend of mine recently bought a well used MS260. We've been working on our chainsaws together every now and then, so we took it apart to inspect/clean.

Turns out the hole for a bolt (right word? maybe not, it's not threaded) that holds a part of the chain brake mechanism is damaged, a part of the 'wall' has broken off.

The bolt/stud/rod/whatever the right name is (sorry, not a native speaker) holds part number 1121 160 5000 in place , which is number 7 on this page from the ipl:

View attachment 1189013


I took a picture:

View attachment 1189025


He mentioned he heard a rattling sound when he ran the saw first time. Turns out that the bolt that was in that broken hole has no groove for a c-clip and was completely loose, and hitting the exhaust.
Possibly it was a replacement, and maybe even the cause of the failure...?

We've been discussing how we might fix this, maybe experimenting (would be a first time) with jbweld or grinding down what's left to have a bigger flat surface to be able to tighten down a threaded rod or a bolt with a low profile head (for the exhaust side).

Does anybody have some advice here? Thx in advance.

Obviously the saw has had a rough life. DIY shows the crankcase that stud is mounted in. It's a press fit and not cheap. I have never seen one break out like that but I guess it could happen as you have one. lol Here is the page and it is item No. 1
https://www.diyspareparts.com/parts/stihl/diagrams/ms260c/a54747b0-c97a-49ed-ad82/

 

[freeasaburt]

Thanks, but the saw isn't valuable enough to justify buying a new crankcase, P/c aren't in super shape either (not terrible, though).
I'm talking to a buddy of mine who might be able to weld it, otherwise would like to find a crankcase from a donor saw; last option is having no working chain brake but not too fond of that idea.

 

[Vintage Engine Repairs]

As Alex said, to make a safe and reliable fix you need a machinist. Mill that area flat to the body of the case then turn an insert with a threaded portion with bolt and washer on the backside. Don’t use JB weld on safety critical parts

I’d suggest replacing the case with a used one, keep an eye on eBay.

 

[Mad Professor]

It's as much work trying to fix it as replacing the case. And the fix won't be as good.

 

[muddy42]

This might be a forlorn hope, but can you get behind it or is it a blind hole? If the former, you could put a bolt in from behind to attach part 1121 160 5000 to.

 

[freeasaburt]

As Alex said, to make a safe and reliable fix you need a machinist. Mill that area flat to the body of the case then turn an insert with a threaded portion with bolt and washer on the backside. Don’t use JB weld on safety critical parts

I’d suggest replacing the case with a used one, keep an eye on eBay.

We were indeed considering something along those lines, thx!
If the area could be flattened enough, we might be able to tighten the bolt from both sides, relieving the 'sideways' stress somewhat.

This might be a forlorn hope, but can you get behind it or is it a blind hole? If the former, you could put a bolt in from behind to attach part 1121 160 5000 to.

Yup, it's an open hole, the bolt sticks through the case (that's why it was rattling against the exhaust).

 

[muddy42]

We were indeed considering something along those lines, thx!
If the area could be flattened enough, we might be able to tighten the bolt from both sides, relieving the 'sideways' stress somewhat.


Yup, it's an open hole, the bolt sticks through the case (that's why it was rattling against the exhaust).

Great, I'd try and get a bolt behind it. Ideally with the widest head possible to spread the load, as the case is already weakened. You could even dent in the muffler a bit to give you a bit more room. This is on the basis you are going to use the saw rather than sell it! Also Id go really easy on the chain brake afterwards.

Do you think that's how the brake was broken in the first place - slamming the brake on too hard?

 

[freeasaburt]

Could be, but as the rod that was in there has no groove for the c-clip, it's also possible that somebody messed with the saw before and fitted a wrong one, possibly a bit too narrow (I'm not at home atm so can't check).

 

[freeasaburt]

I only realised this now, but unless I'm mistaken the broken off piece wasn't in there. So somebody must have been in there, it's a shame the seller didn't mention it...

 

[Tobystihl]

Looks like a case of magrot has set in! A small nut and bolt will suffice with a bit of fettling.

 

[thompsoncustom]

I'm talking to a buddy of mine who might be able to weld it, otherwise would like to find a crankcase from a donor saw; last option is having no working chain brake but not too fond of that idea.

How does he plan on welding it? I'm not sure what magnesium alloy Stihl uses but I'd be surprised if you could braze it without the case melting let alone weld it.

 

[freeasaburt]

Well, we were discussing it, not sure it would actually work. 'Sources online' claim that it isn't that different from welding aluminium; I read that it should be possible with a TIG welder at low temperature, with AZ92 welding wire.
He mentioned that it might be possible to gradually add small layers to replace the missing material, then machine it into shape (Hope I explained that correctly, not a welder myself).

The saw's owner found a 026 carcass online though, he is messaging with the seller. If he buys it and that case turns out to be ok, we might go that way (or still try to repair the current one first and replace it if that fails, we'll see...)

 

[thompsoncustom]

Ya it is possible to do with a Tig welder and if your buddy is a skilled tig welder it's worth a shot.

 

[freeasaburt]

I've seen quite some of his work (on cars, for example) and in my opinion he's a skilled and versatile welder. We'll see how it goes!
Looking for donor saws atm, also for my 044.
I have two 026's and my buddy now this MS260, can't hurt to have some spare parts/donor saws at hand.

 

[Wizard]

A friend of mine recently bought a well used MS260. We've been working on our chainsaws together every now and then, so we took it apart to inspect/clean.

Turns out the hole for a bolt (right word? maybe not, it's not threaded) that holds a part of the chain brake mechanism is damaged, a part of the 'wall' has broken off.

The bolt/stud/rod/whatever the right name is (sorry, not a native speaker) holds part number 1121 160 5000 in place , which is number 7 on this page from the ipl:

View attachment 1189013


I took a picture:

View attachment 1189025


He mentioned he heard a rattling sound when he ran the saw first time. Turns out that the bolt that was in that broken hole has no groove for a c-clip and was completely loose, and hitting the exhaust.
Possibly it was a replacement, and maybe even the cause of the failure...?

We've been discussing how we might fix this, maybe experimenting (would be a first time) with jbweld or grinding down what's left to have a bigger flat surface to be able to tighten down a threaded rod or a bolt with a low profile head (for the exhaust side).

Does anybody have some advice here? Thx in advance.

Here's my 2 cents from looking at this. If it were the only game in town, I would machine off the tower flat to the case, buy or machine a suitable sized stud (pin) to fit hole, drill or ream hole if necessary to fit stud, then lock nut, double nut (if space available), or red locktite threaded nut to threaded stud to hold stud to case.

The tower only provided lateral support to the pin (and perhaps distancing).

I suppose this could have been factory engineered differently.