Carbon on piston tops - clean or not? If so, how?

[tboydva]

Been reading quite a bit about having some carbon buildup on pistons throughout this forum. This is a new motor (for me) and I'm giving it a good once-over with the idea of repowering with it next spring. The head gasket had an itty-bitty leak so I decided to remove it and replace. Now that I can see the pistons, I've noticed a carbon buildup on the surface. Seems like the consensus on this board is that it should be removed. I've decarbed my other motor using the protocol suggested here. Not sure how it has worked (haven't looked inside).

Here's what I see in this motor... So the question is how do I remove this carbon buildup? I sprayed it with seafoam, but it doesn't seem to remove it alone. Should I use some form of abrasive? Wire wheel? I can still see the "ridges" on the top of the piston, so I'm worried about scratching it... I can't seem to find any advise for piston cleaning when you have access to it? Can someone advise or point me to a thread I've missed? Thanks!

Tom

 

[Daviet]

Re: Carbon on piston tops - clean or not? If so, how?

Rotate the piston to TDC, use a fine wire brush in a drill. No need to push hard on the brush, it should take it off.
I run Sea Foam all the time to prevent this problem.

 

[Rick.]

Re: Carbon on piston tops - clean or not? If so, how?

Or, if it is running, you could do a decarb and clean them that way. A decarb. sill also help free up rings and such as well as clean the head of carbon. Best of luck. Rick.

http://forums.iboats.com/showthread.php?t=302825

http://forums.iboats.com/showthread.php?t=158076

 

[fire7882]

Re: Carbon on piston tops - clean or not? If so, how?

I'm not sure if this is a big issue or not but when I recently dissembled my power-head, there seemed to be some type of coating on the piston tops. I've seen ceramic coatings on aluminum pistons before to shield them from the combustion heat. If that is the purpose of this coating, I would be careful to not remove it. With the lower compression of these 2 stroke motors, it shouldn't be an issue but if the coating is there, I'd be sure to leave it intact.

Here you can see the piston on the right has a green surface coating. The piston on the left was replaced during a rebuild by a previous owner and doesn't seem to have this coating.

 

[Tig]

Re: Carbon on piston tops - clean or not? If so, how?

Good though about the piston coating, Fire.
I would not manually clean a piston while it is in the engine. The reason being that any carbon you scrape off may get beside the piston where it will be picked up by the compression ring, possibly causing it to stick.
Looking at your pics, they don't look bad at all. IMO
Don't forget to wipe those flakes of carbon off the cylinder wall with a clean rag before you close up.
I like the links Rick posted for decarbon advice. Give that a try and enjoy your new motor.

 

[HybridMX6]

Re: Carbon on piston tops - clean or not? If so, how?

I agree that it doesn't look that bad, and if it were mine I'd prefer to put it back together, wait to repower with it, then do the decarb when the motor is running. It should have no problem removing that amount of carbon.

 

[Jeff_G]

Re: Carbon on piston tops - clean or not? If so, how?

Put a new head gasket on, torque it down and go have fun.
Nothing to worry about. It isn't the carbon on the domes to worry about as it is the coking of the rings. In fact the carbon does help protect the pistons from detonation in some cases.
None of the X-flow motors ever had any coting on the pistons from the factory.
As for keeping the carbon from building up too much use a cleaner like Mercury's Quickleen in your fuel and a twice a year application of Power Tune, or Yamaha's RIng Free.
X-flow engines are particularly suspectable to coking (carbon build up) from the use of cheap oil, and running without thermostats.
While OK, I haven't had spectacular success with Sea Foam, as a marine shop owner I don't carry what Wally World stocks for the most part.

 

[tboydva]

Re: Carbon on piston tops - clean or not? If so, how?

Alright... Not sure what I'm going to do, but the bits of junk visible in the cylinder is some material removed after soaking with seafoarm. I broke a bolt taking off the exhaust cover, so it's off to the machine shop for a few days. I think I'm going to see what I can flake off easily with something not too abrasive (got some off with my fingernail), then probably leave it and seal it back up. I guess I'd rather have too much material on my piston than too little! Thanks for all the help.