Can't slide cylinder off piston of STIHL MS 362

[T.Bird]

Hi! First time rebuilding a saw. I'm doing the top and bottom end (cylinder and piston as well as crank bearings and seals) on a STIHL 362 C. I've got the saw pretty much totally broken down and it has all gone really smoothly until I finally got to taking off the cylinder. I can't get the piston to drop all the way out of it. It's not seized. The piston will slide up and down a bit (I don't think it will twist, but I'm afraid to try too hard.) but it slides down to the point where the top of the piston is just about an 1/8'' below the exhaust port and then it gets stuck. The only thing I've tried so far is sticking a dowel in the spark plug hole and hitting it with a hammer, but no luck. The spark plug doesn't go in straight down though the top center of the cylinder so that doesn't help. Any other ideas? I have no problem with destroying the cylinder and/or piston in order to separate them as they will both be replaced, but I just wanted to check in first and make sure I wasn't missing something obvious.

Thanks!
Tom

 

[Vintage Engine Repairs]

Hi Tom,

What’s the reason for replacing the piston and cylinder? This info may help to make an informed decision / recommendation / diagnosis to your issue.

Regards, Tom

 

[T.Bird]

Hi Tom,

What’s the reason for replacing the piston and cylinder? This info may help to make an informed decision / recommendation / diagnosis to your issue.

Regards, Tom

You’re going to hate this, but the reason is because the service department at the shop that my boss took the non-running saw to told him that it needed a new piston and cylinder, so that’s what he bought. I know… Right???

He also bought new crankshaft bearings. Which leads me to a follow up question: Do I even have a prayer of replacing them without finding someone with the proper crankcase splitting tools?

 

[Mad Professor]

How do the rings look intake and exhaust side?

Broken ring could be hanging up in a port.

Saw shops love to sell new P/C sets.........

 

[Vintage Engine Repairs]

Stihl tech’s have to follow Stihls repair instructions. Which is always the ideal solution, be it at the expense of the customer.

Often times, cylinders can be saved depending on condition.

Without pictures though, we can’t give any proper advice.

Anyway! If you have a new OEM piston and cylinder, happy days! That’s a 400 AUD pair of parts right there.

My advice - take some clear photos through the intake and exhaust port and upload them here.

 

[pioneerguy600]

Yeah, ring hanging up in the intake port if the top of the piston is below the bottom of the exhaust port.

 

[T.Bird]

A broken ring hanging up in the intake port sounds believable. Do these photos help confirm or debunk that theory?

Here are what the rings as seen through the exhaust port:


A here you can see the top of the piston through the exhaust port in it’s “stuck” position:

 

[Vintage Engine Repairs]

We need to look through the intake

 

[T.Bird]

Oh yeah… Not much to see…

 

[T.Bird]

Real tough to get well lit pictures, but I don’t see much to suggest broken rings in there.

 

[Lee192233]

Maybe the circlip is hung in the transfer port?

 

[Woodslasher]

If I had a new top end there I'd say f-it and just yank the cylinder till something came off!

 

[dmezzomo]

Push down on the rings with a small screwdriver thru exhaust port. It should spring in and out if you press it into the ring groove. No spring, probably broken ring.

 

[Bob Hedgecutter]

If I had a new top end there I'd say f-it and just yank the cylinder till something came off!

Not everyone has the hand strength of an Orangutan though?
How about a pair of custom cut tapering hardwood wedges between crankcase and cylinder flange? Keep knocking the boggers in until something lets go!
If you could get the crank to TDC and the piston down as low as you can, could you slip a split beer can between piston and cylinder enough to work past whatever is catching?

 

[lostone]

Someone with better eyes? first pic of exhaust port, top ring right side.

 

[Woodslasher]

Someone with better eyes? first pic of exhaust port, top ring right side.

Looks like a busted ring or maybe the gap where the locating pin should be.

 

[lostone]

Looks like a busted ring or maybe the gap where the locating pin should be.

I wasn't sure, my eyes aren't that great anymore, wondered if it was a locating/gap that the pin sheared or fell out and allowed the ring to spin. But you are thinking the same thing.

 

[lostone]

Look at the square edges on the lower ring, then look at the upper ring, it's rounded on the edges. I'm wondering if somehow that ring has been spinning and catching on the ports rounding the edges off. I'm GUESSING again but looking down the spark plug hole and wondering if the walls on the cylinder are chewed hard meaning there's no saving that cylinder??? pure speculating on my part at this time.
It could also be like Woodslasher said and be a busted ring, This would allow the upper ring to tilt as it was passing by the exhaust port and wearing in such a manner as showing and tbh probably a more realistic thing to happen than the ring spinning. Either way I would be GUESSING again that if the ring was catching that hard the the liner on the cylinder is chewed away above and below the exhaust port.

 

[T.Bird]

Any thoughts on how to actually get it out?

 

[Smitty Smithsonite]

I noticed that little divot in the top ring, too, like a chunk has bee taken out of it. I also noticed some heavy scoring in between the transfer ports looking into the cylinder from the exhaust.