MS 360 Repair (Help needed)

[jensent]

Have an MS 360 that scored the piston and cylinder on the exhaust port side. Have replacement parts. Could sure use any and all advice from those who have experience with this type of rebuild. I am assuming it went lean to damage the p&c in that area. What steps would you take to prevent this from happening again. Haven't found anything obvious. Are there lubs that should be used in the assembly. I don't want to fire it with the cylinder walls dry do I?
Thanks
Tom

 

[Freeheat]

I use 2cy oil on the walls for a pre-lube , make sure you clean and adjust the carb

 

[rkshed]

I always lightly lube the walls with premix when reassembling. The argument has been lubed causes glazing on start up and therefore takes longer to seat the ring/rings.
I'll take the chance and after 30+ years, I haven't had a failure from it.

 

[jensent]

Thanks, the more suggestions the better I feel. So Smokin' Jay and the rest jump in!
Tom

 

[Angelo C]

Have an MS 360 that scored the piston and cylinder on the exhaust port side. Have replacement parts. Could sure use any and all advice from those who have experience with this type of rebuild. I am assuming it went lean to damage the p&c in that area. What steps would you take to prevent this from happening again. Haven't found anything obvious. Are there lubs that should be used in the assembly. I don't want to fire it with the cylinder walls dry do I?
Thanks
Tom

What do you consider "the replacement parts" we can start from there. If its just the piston, rings and cyl then we need to chat some....about the case gasket set, bearings and hoses that all should be gone through too. All after we confirm what caused the lean burn in the first place.

 

[jensent]

What do you consider "the replacement parts" we can start from there. If its just the piston, rings and cyl then we need to chat some....about the case gasket set, bearings and hoses that all should be gone through too. All after we confirm what caused the lean burn in the first place.

Ok Angelo if your willing I need guidance. Have piston, cylinder, ring, pin, c-clips and base gasket. What else do you think we should replace or test before assembly? Also how do we test our work as we progess and when we finish to see if there are air leaks. How do we find what caused the lean burn? Anyone who wants to jump in is sure welcome.
I think it over-heated when my 250lb son leaned on it with a chain that would only throw dust in a 40in red oak until the saw quit.
Tom

 

[Angelo C]

Start with pressure and vacuum testing everything that looks like a hose or has a hose attached to it before you break it down. Make sure the case hold pressure and the bearings are smooth and the bearing seals are...um sealing. Can you post a pic of the cyl ?

 

[MasterMech]

Block/seal the exhaust and intake ports. Make sure the decomp valve is closed and there is a spark plug in it. There are special tools to connect a vacuum/pressure pump to the engine, most of the time you can just hook onto the impulse line port. You want to apply a bit of pressure, then vacuum and make sure it holds. Soapy water will find any leaks that show up under pressure.

Visually confirm the condition of the impulse line and intake boot. No cracks or punctures are permissable. In fact, both the impulse line and fuel line/filter should be replaced at this time without question. Confirm the carb is ok with a "pop-off" pressure test or just do a gasket/diaphram kit there too. No need to split the case unless something is wrong with the bearings or case gasket.

This all can and should be done with the old piston & cylinder in place. Then repeat after the engine is reassembled.

 

[Angelo C]

Block/seal the exhaust and intake ports. Make sure the decomp valve is closed and there is a spark plug in it. There are special tools to connect a vacuum/pressure pump to the engine, most of the time you can just hook onto the impulse line port. You want to apply a bit of pressure, then vacuum and make sure it holds. Soapy water will find any leaks that show up under pressure.

Visually confirm the condition of the impulse line and intake boot. No cracks or punctures are permissable. In fact, both the impulse line and fuel line/filter should be replaced at this time without question. Confirm the carb is ok with a "pop-off" pressure test or just do a gasket/diaphram kit there too. No need to split the case unless something is wrong with the bearings or case gasket.

This all can and should be done with the old piston & cylinder in place. Then repeat after the engine is reassembled.

We are talking about enough pressure/vac to fill a basketball not a truck tire...8-10 lbs max. Also rotate the flywheel a few times while it's under pressure, sometimes the seals elongate and don't reveal the leakage w/o a turn or two. A mity vac brake bleeding tool can usually be borrowed at autozone for free. They take a credit card for deposit and return your money when you return the tool. You can buy a decent compression tester there too. Make sure you get one with a release valve at the head.

 

[jensent]

Saw is already apart. Suggestions?

 

[MasterMech]

May as well put the top end back together then (with new parts) and do your leak test once it's together. You don't have to split it or pull it apart again to change those seals should they need it. I would however, check the bearings for play (radial and axial) while it's apart.

 

[jensent]

Guys, need answer to this question. New piston has an arrow on the top at an edge. Does this arrow note the intake (carb) side or the exhaust (muffler) side?

 

[Boog]

Guys, need answer to this question. New piston has an arrow on the top at an edge. Does this arrow note the intake (carb) side or the exhaust (muffler) side?

Exhaust side, that way the ends of the rings are on the wide solid side of the cylinder, otherwise the ends of the rings will catch on the ports if installed the other way.

 

[StihlHead]

Arrow always goes forward toward the exhaust (direction of air flow).

 

[jensent]

Thanks. I'll keep you posted as to the outcome.
Tom

 

[jensent]

Sorry I didnt follow with info on the rebuild. Finished rebuild without problems. Thanks to all who helped. Saw popped on 3rd pull, started on 4th. Ran it for about 30min, no load. Cut with it for about 15min at various engine speeds. Had dealer adjust carb and check top RPM. Now waiting for a truck load or two of wood from the local tree service.
Thanks again!
Tom

 

[Angelo C]

Did you find out what the cause of then lean fire was?

 

[jensent]

When the dealer rebuilt the carb he said that the impulse side was full of very fine dust. We had been using that saw to buck several 40 ft sections of dry dead standing red oak. Fresh chains produced more dust than chips even when new. I have found others having the same P&C problems with the 360,361,362 in dry dead wood on the arborist site. Stihl does show two different air filters for that saw. One is fabric for normal operating conditions. The other is a fleece filter(non-woven) for dry and dusty conditions. We had used the fabric. Has anyone used the fleece filter and what was your impression?
Tom

 

[MasterMech]

I run the fleece filter on my 034 and whenever it was time to clean it, the inside of the filter and the carb bore are clean as a whistle.

 

[rkshed]

Does Stihl recommend adjusting the carb when changing to a tighter filter?
I ask this because unless the surface area of the tighter filter is greater than the original, in theory, it will run a bit lean. Less air means you need to richen it up.
Maybe the new fleece filter is more or less just like putting mom's old nylons over your air filter. Then the air intake really wont be changed until it starts to get coated with dust.
Just curious...

 

[smokinj]

Does Stihl recommend adjusting the carb when changing to a tighter filter?
I ask this because unless the surface area of the tighter filter is greater than the original, in theory, it will run a bit lean. Less air means you need to richen it up.
Maybe the new fleece filter is more or less just like putting mom's old nylons over your air filter. Then the air intake really wont be changed until it starts to get coated with dust.
Just curious...

You should adjust carb when needed....

 

[Bigg_Redd]

Have an MS 360 that scored the piston and cylinder on the exhaust port side. Have replacement parts. Could sure use any and all advice from those who have experience with this type of rebuild. I am assuming it went lean to damage the p&c in that area. What steps would you take to prevent this from happening again. Haven't found anything obvious. Are there lubs that should be used in the assembly. I don't want to fire it with the cylinder walls dry do I?
Thanks
Tom

1) don't straight gas it

2) make sure your carb is tuned somewhere in the factory specification ball park

3) coat everything with 2 stroke oil during reassembly

 

[MasterMech]

Less air means you need to richen it up.

I think you got that backwards.....

 

[rkshed]

I think you got that backwards.....

Yah, yah! Crap! Sorry about that!
I just spaced that one.
Still, don't you need to adjust the carb or is there no effect at all?

 

[MasterMech]

Yah, yah! Crap! Sorry about that!
I just spaced that one.
Still, don't you need to adjust the carb or is there no effect at all?

I would run the saw and see how it sounded. Maybe tweak it a bit if I felt froggy but if my ear says all is good, I don't worry.