Stihl MS361 scored piston

[Timgunner]

I bought a Stihl MS361 at a farm auction a couple weeks ago. It looked very dirty and went for what I thought was a good deal. After paying the fees and my gas to go pick it up I was in the saw for $300. Not bad, I thought especially when I cleaned it up and it was just dirty with dust that cleaned off to reveal a nice looking saw. Unfortunately when I tried to test the saw it would start but not idle and when the throttle is applied it dies. I thought it was a carb issue so I took it into the dealership and they are telling me it has a scored piston and the parts and labor are $400 plus tax to get it running again. I’m pretty unhappy with the auction company who listed the saw as “good running.” What should I do? There’s no way I’m paying $400 to fix it. I’m thinking of fixing it myself with an aftermarket piston and cylinder kit. However I’ve heard that possibly the cylinder might be still good and can be cleaned up with some kind of acid? Then I could get a new OEM piston and rings and put it back with OEM parts. I haven’t picked up the saw yet so I don’t know what the cylinder looks like. How do I tell if it is salvageable and what kind of acid do I need and where do I get it?

 

[Chevboy0167]

Time to tear into and look for damage...

 

[snobdds]

A 361 is one of the best saws ever made. It would be worth it to fix it up with OEM parts. It will last another 15 years if taken care of properly.

 

[mbrick]

What kind of terms does the auction company offer?

I would ask them for the cost of an OEM P&C and do the work yourself. Seems like a fair compromise.

Seconding others feedback about using OEM parts. You may need just a piston.

 

[Timgunner]

What kind of terms does the auction company offer?

I would ask them for the cost of an OEM P&C and do the work yourself. Seems like a fair compromise.

Seconding others feedback about using OEM parts. You may need just a piston.

I read the terms and conditions and the auction site puts full responsibility on the seller and buyer for all things so there’s no hope of getting anything from them. I’m hoping i can reuse the cylinder and find a good non-dealership OEM piston somewhere. Is eBay a trustworthy place to find a new old stock OEM part?

 

[The Shooters Apprentice]

I rebuild a MS361 with a Farmertec big bore kit and was happy with those parts.

 

[Woodslasher]

Meteor piston kits are excellent quality and very affordable, I'd get one of them.

 

[Chevboy0167]

I have had good results with the Meteor brand.

https://www.ebay.com/itm/1718650891...PsoFEF7vPHqCLL7Xng0yHEcyY=|tkp:Bk9SR6zkxNqKYQ
https://www.meteorpiston.com/shop/c...-cylinder-chainsaw-stihl-361-o-47-33917#attr=

 

[Chevboy0167]

Ouch!!!

https://www.ebay.com/itm/2338941417...DIW0MXulcOlIj6CuTi9zNwgwQ=|tkp:Bk9SR-CIlduKYQ

 

[huskihl]

Any pics of your original cylinder?

 

[Timgunner]

I just picked up the saw. The tech left the muffler off and the piston looks really bad through the exhaust port. I’ll pull the head off when I get home and see what the cylinder looks like. Here’s hoping it is still usable

 

[Timgunner]

Well I’m pretty surprised at the condition of the cylinder it doesn’t look anything like the piston. The piston looks terrible!

 

[Timgunner]

I think the cylinder looks salvageable what do you guys think? Looks like a little transfer and no scoring through the nikasil coating

 

[huskihl]

That’ll clean up it looks like

 

[Timgunner]

So my question is what causes the piston to get trashed on the exhaust side?

 

[huskihl]

So my question is what causes the piston to get trashed on the exhaust side?

Overheating from a high air to fuel ratio. Too much air (air leak) or too little mix (H screw turned in too far)

 

[Timgunner]

The o-ring seal is all cracked where the top of the carb mates with the plastic plate that the air filter mounts to. Could that cause enough air leaking to run lean and trash things?

 

[huskihl]

The o-ring seal is all cracked where the top of the carb mates with the plastic plate that the air filter mounts to. Could that cause enough air leaking to run lean and trash things?

Not likely. A bad fuel line/filter, stiff diaphragms in the carb, impulse line, intake boot, crank seals, base gasket, ir it was tuned too lean. The adjustable jets are there to use as conditions change. Different oil/fuel, temp changes, slightly stiffening diaphragms…all would require slight tuning. Failure to notice the lean running condition results in what you have

 

[Timgunner]

Not likely. A bad fuel line/filter, stiff diaphragms in the carb, impulse line, intake boot, crank seals, base gasket, ir it was tuned too lean. The adjustable jets are there to use as conditions change. Different oil/fuel, temp changes, slightly stiffening diaphragms…all would require slight tuning. Failure to notice the lean running condition results in what you have

The fuel line does have holes in it and it was leaking fuel

 

[huskihl]

The fuel line does have holes in it and it was leaking fuel

That’ll do it. But it needs to be understood that it’s the operator that ignored the symptoms and allowed it to burn up. A saw needs to burble with no load and clean up in the wood. If it screams with no load, it won’t live long