MS 880 Given to Me

[PP4218]

So a friend of mine gave me his MS 880. He couldn't get it to start so he took it to the Stihl dealer. They said he needed a carb, piston, and cylinder. He said forget it and put it in his basement.

Well he gave it to me and sure enough, the piston is scratched badly on the exhaust port. The intake side has one grove, but it fails the fingernail test. I've got a new cylinder, piston and rings, and a decomp valve for it. Also a carb, but I think the carb on it is fine (OEM) as it is new. Oh, and he caught the cover on fire too.



Anyway, what do you guys recommend for a cylinder base gasket and exhaust gasket?

 

[user 122190]

I just sold mine. It is at the top of the food chain. OEM on everything.

 

[cookies]

he ran it often with the brake on or it was full of trash holding it on. Check all of the brake assembly, clutch, drum and crank bearing/seals very carefully.

 

[thomasinvancouver]

If you don’t want it, let me know and I’ll dispose of it for you. Damn myself for being so selfless.

 

[PP4218]

What would cause the exhaust port skirt to be so scarred up?

 

[Yukon Stihl]

You should do a vacuum and preasure test to find out why the original piston scored.

 

[Thommo]

What would cause the exhaust port skirt to be so scarred up?

By the looks of the area around the clutch i would say the crank seal is melted too. You most likely have a bad vacuum leak from the clutch side crank seal

 

[PP4218]

You should do a vacuum and preasure test to find out why the original piston scored.

I have one of the little "pushbutton" type of testers for vacuum and pressure. It goes to 15 or 20 psi - I've only used it to check fuel lines and floats though in my two stroke lawnboys from the early 80's. Thanks for the tip!

I'm doing more of a teardown today on it so I'll make sure to check those seals too

 

[PP4218]

Well, I'm having a problem setting up for the leak down test. This MS 880 has the aluminum muffler with the clip versus the screw down. Any thoughts on the best way to seal the exhaust port?

Also, I am having trouble finding a cover replacement for the burned chain brake cover. Will parts from an old 084 chain brake cover fit on this MS 880?

 

[mbrick]

What a score of a project saw! Others are on it with the feedback – all OEM parts, replace all rubber bits, hoses, etc that are likely hard.

Yes, needs to pass a vac test then pressure test (in this order) so you know it won't score the piston again. Stihl service manual details pressures, time, etc.

 

[BrettS]

Gave you!, would sure be nice if I had friends that gave me stuff like that.

 

[Kodiak Kid]

My. Neighbor traded me his perfectly good running 088 for two cords of un split fire wood Stihl in the round! Being as good dry firewood is plentyful where I live. I made out like a champ on that one I'll tell ya!

 

[PP4218]

I have figured out a new way to seal the cylinder ports (patent pending). I hope to complete the final testing of the prototype today and then use it to test the saw for vacuum and pressure leaks.

 

[PP4218]

Well, I completed my testing and the saw passed the vacuum and pressure testing just fine.







10 minutes for each test. No changes. I rotated the crank with the pull start and observed movement on the needle, but no changes in absolute numbers. Very pleased with the results.

 

[PP4218]

What do you guys think of this cylinder scoring?

 

[PP4218]

More pictures:

 

[PP4218]

And here is the piston:






Top ring is stuck - seems to have been overheated. Intake side has very light scratches, but nothing severe. Exhaust side took all the damage.

 

[PP4218]

Okay, so now that you guys have seen the cylinder and the piston, what do you think about sanding the cylinder and reusing the cylinder with a new piston and rings?

If you think I should sand this out, what grit do you find appropriate to start with, and then finish with?

I do have a new cylinder, but it is not OEM (chrome plated bore) and a new piston (also non-OEM). The new cylinder has provisions for a bolt on muffler, but I have the cast aluminum one that clips on.

So, what say you?

 

[mbrick]

Can you tell if there is any plating damage in the cylinder? Any grooves you can catch gently moving a pick across them?

I had one recently that I could tell with a pick the raised aluminum vs small grooves/scores through the plating. So I bought a new OEM cylinder and piston so it would be mint.

Your cylinder looks like it could be ok... Try 800 or higher to start? I'm not an expert here.

I do see one small missing plating spot near one of the ports but that may have been a manufacturing defect...

Also a difference between "will work" and a proper restoration for a deserving saw like this. It should have all OEM and fresh parts.

 

[rogue60]

It's an expensive saw... And you got the saw for free and you don't want to spend any money on it and you are completely happy to do a dodgy rebuild on... why even bother?
My advice Put In a box and sell it on.
The next guy will enjoy and take pride in his work rebuilding it correctly value adding to the saw using OEM parts.
Just saying...