346xp OE Peek @ piston. Look OK?

[Engineeringnerd]

After 18 years of running this saw, the saw's tune was starting to wander and require constant adjustment. Figuring it was likely either the carb needing a rebuild or an air leak, I changed out the carb, replaced the fuel line & filter, and inspected the intake boot for air leaks (already changed to metal clamp). Decided to take a look at the cylinder and piston while "in there". Even though its an older saw, it hasn't seen a ton of hours. What do you guys think of the condition of the cylinder??

 

[Engineeringnerd]

Also.... there is a small vent (see where forceps are pointing" that looks like a hose goes there, but it wasn't occupied. Is something supposed to fit on this nipple, or is it just a bare vent? Other than knocking something loose while cleaning the saw, I don't remember there being anything connected to it.

 

[Aknutter]

Need to move this to chainsaw in the equipment forum. There you'll get plenty of traffic. Maybe the moderator @les-or-more can move it for you.

 

[les-or-more]

Moved.

 

[rob066]

Whats that dent on top of the piston.

 

[huskihl]

Also.... there is a small vent (see where forceps are pointing" that looks like a hose goes there, but it wasn't occupied. Is something supposed to fit on this nipple, or is it just a bare vent? Other than knocking something loose while cleaning the saw, I don't remember there being anything connected to it.

Nothing went to the nipple on the older saws.
I’d remove/clean the tank vent and reinstall. And put a new 42mm Caber ring in it. Maybe try to remove the carbon on the sides of the piston with scotchbrite pads

 

[dave ensign]

If it was my saw, it would get a new top end kit. Your piston is ashtray material and photo of the cylinder is
questionable. Seal and metal boot clamp. Good for another 15 years. Great Saw.

 

[mbrick]

If it was my saw, it would get a new top end kit. Your piston is ashtray material and photo of the cylinder is
questionable. Seal and metal boot clamp. Good for another 15 years. Great Saw.

And here I was thinking both the piston and cylinder show original machining marks on the piston and crosshatch in the cylinder so they look great.

The top of the piston makes me think the saw is tuned lean though. No piston wash.

OP I would have cleaned the saw more before pulling the cylinder. Full cleaning of all loose debris before removing anything. I see plenty of debris right around the edge of the opening... fortunately its mostly wood and not dirt I guess?

After that many years I would definitely put a OEM kit in the carb. Will help a lot. And vac/pressure test to confirm crank seals and what will now be a new base gasket are sealing.

 

[dave ensign]

The blow up of the piston showing the wrist pin looks like the ring grove is burnt away.

 

[mbrick]

I see what you are referring to. I think it is a figment of the camera focus but absolutely worth clarifying.

 

[Dudley220]

Clean the carbon up put a new ring on it set the squish with the right thickness of gasket new intake boot clamp pressure check and check the rubber in carb and run it for another 15 years

 

[bwalker]

If it was my saw, it would get a new top end kit. Your piston is ashtray material and photo of the cylinder is
questionable. Seal and metal boot clamp. Good for another 15 years. Great Saw.

The saw appears like it got hot at some point or it was ran on crap oil hence the deposits, but the piston and cylinder look fine.
I'd re ring, reassemble and test for air leaks.

 

[Jonny Quest]

Clean the carbon up put a new ring on it set the squish with the right thickness of gasket new intake boot clamp pressure check and check the rubber in carb and run it for another 15 years

+1

 

[BrettS]

Whats that dent on top of the piston.

I would say from a metal piston stop.

 

[Engineeringnerd]

Whats that dent on top of the piston.

Thought it was a shadow from a carbon lump, but it looks like a small dent, likely not new as it has a carbon layer on it. Perhap from using a screw in piston stop to change the clutch mechanism.

 

[Engineeringnerd]

Nothing went to the nipple on the older saws.
I’d remove/clean the tank vent and reinstall. And put a new 42mm Caber ring in it. Maybe try to remove the carbon on the sides of the piston with scotchbrite pads

Thanks Huskihl

 

[Engineeringnerd]

If it was my saw, it would get a new top end kit. Your piston is ashtray material and photo of the cylinder is
questionable. Seal and metal boot clamp. Good for another 15 years. Great Saw.

Already put on the metal boot clamp, had a major leak about 10 years ago. was running good, so may go with the simple ring change, cleanup, and wait for performance to drop before putting in a new, larger top end.

 

[Engineeringnerd]

Thanks guys. The saw ran good before taking apart, I was taking a peek to see what it looked like. The carb was drifting all over the place and the last time I ran it it was really lean and couldn't adjust it out. Changed out the carb, changed out fuel line, and checked the intake seal which fixed the problem. Maybe a new top end next time I'm in or feel performance lacking. Ran great once back together with the new carb. I'll have to study up on how to do pressure testing and squish mod; haven't been
there before but have watched Iron Horse do it on a 372 using motorcyle assembly silicone after removing the gasket. Didn't look like rocket science.

 

[Vintage Engine Repairs]

Piston looks fantastic, machine marks are still there.

Gently clean off the carbon with some fine scotch brite and treat it to a new ring.

scotchbrite the cylinder walls too.

pop the c-clips out and inspect the small end bearing, replace it if you’re unsure.

New c clips, clean the gudgeon pin and finish off with a pressure and vac test. New carb kit, lines and filter and it will last another 20 years.

 

[TRTermite]

Piston looks fantastic, machine marks are still there.

Gently clean off the carbon with some fine scotch brite and treat it to a new ring.

scotchbrite the cylinder walls too.

pop the c-clips out and inspect the small end bearing, replace it if you’re unsure.

New c clips, clean the gudgeon pin and finish off with a pressure and vac test. New carb kit, lines and filter and it will last another 20 years.

Correct me if i am just babbling, BUT after you use the scotch brite do a thorough cleaning. Forgot you already have it back together.. Next reader may benefit.