346xp cylinder question

[hellomyles]

So I started my 346xp project today. I just got this saw and is in very good cosmetic shape and looks to be hardly used. I started to clean it and begin porting and took the cylinder off to inspect things and it has a mark on it by the exhaust port. I don’t see anything on the piston that shows signs of damage. And the piston looks brand new. Which it might be. You can feel the problem spot with your finger nail. It’s not terrible but wondering what I should do. It seems like the ring will hang on it eventually. And cause damage or compression loss. Let me know what you guys think.

 

[hellomyles]

Also one of the exhaust bolt threads in the cylinder is stripped so I assume someone was in this recently. Which is fine just trying to see what I should do.

 

[RIDE-RED 350r]

Is that mark lighter in color because the plating is gone leaving the aluminum cylinder casting visible???

 

[ny15]

Looks like someone cleaned some transfer off of that cylinder and put a new piston in it. I agree that it looks like the plating has flaked off in that spot.

 

[sunfish]

Rub on it with a little 220-320 sand paper and see what happens. Being below the port it's likely not an issue, but? New oem P&C is around $120 btw.

 

[hellomyles]

Is that mark lighter in color because the plating is gone leaving the aluminum cylinder casting visible???

I just went and looked at it again and it appears to be. Looks like the nikisil is gone in the light colored spots and is down to the rough casting.

 

[hellomyles]

Rub on it with a little 220-320 sand paper and see what happens. Being below the port it's likely not an issue, but? New oem P&C is around $120 btw.

I just took a pick and ran it over the spot and it’s definitely a low spot where the problem area is. Looks like the nikisil is gone. And it’s down to he casting. Do you think that it will cause an issue with time? Probably better to replace the cylinder...

 

[ny15]

If it was me I’d find a used OEM cylinder to port.

 

[RIDE-RED 350r]

Myself, I would not use that cylinder. Others may use it. Or you could give it a try and if it lasts, great. If not then you will have to do the cylinder kit. Only risk with that approach is that a catastrophic failure could send debris to the bottom end and damage crank bearings or the case. Your call.

 

[hellomyles]

If it was me I’d find a used OEM cylinder to port.

Would you stick with the 45cc OE? Or bigger bore?

 

[hellomyles]

Myself, I would not use that cylinder. Others may use it. Or you could give it a try and if it lasts, great. If not then you will have to do the cylinder kit. Only risk with that approach is that a catastrophic failure could send debris to the bottom end and damage crank bearings or the case. Your call.

Yeah that’s kind of what I was thinking. Don’t really want to take out the bottom end due to a little money to fix it right.

 

[ny15]

I’d stick with a used OE. It comes down to what you want to spend on the saw. It obviously had an issue to begin with to cause the original piston failure. If that piston is a Meteor I would use it and find a used OEM cylinder. If it’s not a Meteor I would buy a new p&c kit. But first and foremost I would bolt the original cylinder back on the saw and perform a pressure and vacuum test to determine if there’s an air leak . It’s very possible the stripped exhaust bolt caused the muffler to loosen up and that caused the failure.

 

[Ryan Browne]

Would you stick with the 45cc OE? Or bigger bore?

Either way, from my understanding. Some guys really like the OE. I think it was rated at a higher max RPM. More of a purpose built limbing saw. The NE has more grunt though.

Edited to add: if you decide to go NE, and that's a meteor, I'd give you a few bucks for it. I'm gonna need one for the OE I just picked up.

 

[RIDE-RED 350r]

Would you stick with the 45cc OE? Or bigger bore?

If going new, hard to not get the NE kit. Easy bolt-on boost IMHO. If going used, I'd grab the first thing that pops up for a price you like. The OE's do run well too.

 

[blsnelling]

That cylinder will be fine. Run it as is. In no way does this pose a risk for a catastrophic failure.

 

[hellomyles]

I’d stick with a used OE. It comes down to what you want to spend on the saw. It obviously had an issue to begin with to cause the original piston failure. If that piston is a Meteor I would use it and find a used OEM cylinder. If it’s not a Meteor I would buy a new p&c kit. But first and foremost I would bolt the original cylinder back on the saw and perform a pressure and vacuum test to determine if there’s an air leak . It’s very possible the stripped exhaust bolt caused the muffler to loosen up and that caused the failure.

Yeah I will vac and pressure test it when I get the porting done. [emoji106]

 

[hellomyles]

That cylinder will be fine. Run it as is. In no way does this pose a risk for a catastrophic failure.

Alright. I am just gonna port this one and run it!

 

[drf256]

Someone cleaned that cylinder up quick and added a meteor. A few points:

That’s a loss of plating. See the coarse scrathes in the plating below the Ex floor? That will eat up a piston skirt fast. The coarse Nikasil will grind the aluminum down. If you look at your piston, it’s already starting to. Look at the fine scratches on the skirt.

You can run that jug. You’ll need to sand it with a finer grit. I’d personally get a scotchbrite drum and use it. First, wrap it in the new 320 grit 3M clear backed wetordry sand paper. Go in a direction that will keep it wrapped. WD40 in the cylinder, then hone it with the 320, moving up and down. When you’re done, wash and dry, WD40 again, then home with the scotchbrite drum itself. I find that purple is a good start, then finishing with the fine grey.

I’m not that familiar with the model, but I bet the ring/crown of the piston is above that area at BDC. It won’t affect compression at all, and there is enough plating on the sides of it to support the skirt and/or ring.

If the finish above the Ex roof stays intact after the above, I’d use it.

Post some pics when you are done.

 

[XP_Slinger]

That cylinder will be fine. Run it as is. In no way does this pose a risk for a catastrophic failure.

Brad, does the ring drop below the exhaust port on a 346?

 

[Gary Courtney]

Would you stick with the 45cc OE? Or bigger bore?

I went bigger on the two I re-built. New p/c,oem all the way.