Carbon on pistons

Hey everyone
I'm in the process of replacing all my engine gaskets. I'm looking at the pistons and noticing some carbon buildup on the tops. I showed a picture to the guy at my local shop who said it wasn't worth replacing the pistons over. I'd prefer everything inside the engine to be clean when I put it all back together, but it's not worth the 300 bucks for new pistons. Is there a way to clean it up the deposits on the tops of the pistons before I start putting it back together?

YES. Just be very careful not to allow any of the carbon residue down the sides of the piston at the cylinder wall. You can pack some paper towel material around the perimeter of the piston an scrape the top of the piston with a popsicle stick. Vacuum after to make sure nothing gets down the sides.

BTW, that carbon buildup is normal and will be there again in a few thousand miles after you clean it off.

Piic?
Steve

Here's a pic of it. The cylinder block is removed now and is being honed at the shop. I just want to clean them up a little so I dont get any carbon bits inside my clean cylinders

New rings? That's carbon/normal. How about your valves and seals?
Steve

that doesn't look bad at all. If you've got the cylinders off and honed then pull the wrist pins and clean up your pistons before replacing the rings. Avoid cleaning the pistons over the cases, its easier to clean the piston tops and ring grooves on the bench and you risk getting less contaminants in the engine.

Follow the factory manual for cleaning and inspecting the pistons and installing the rings.

Getting back to basics for a minute, what was the problem that lead you take the engine apart? Smoke/oil consumption, low compression?

I'm planning on reusing the rings. The valves and seals are in good shape. I'm taking the engine apart to replace all the gaskets because it was leaking oil from the head. I figured I'd do them al to avoid breaking it back down to the base when that finally goes. If the carbon is normal and will return fairly quickly, I'm debating just blowing the tops with compressed air and reinstalling the cylinders.

how many miles? Valve guide seals and rings. IMO
Steve

As the service manuals always say, it's never going to be easier to replace the rings than it is right now. If you're having the cylinders honed you might as well take the pistons off and clean them (there's no easy way, but carb cleaner and a scotchbrite type pad will get you most of the way, doesn't have to be perfect, you just don't want flakes or an uneven surface) (careful not to drop those circlips in the crankcase!). Check the piston wrist-pin wobble, measure everything with calipers as the book says to. Write it all down. That way you'll have some idea of how close you are to needing an overbore. Definitely put in new valve seals. As long as you have the head off you might as well lap the valves... Did you measure your clearance before tearing it down? Any shims getting too close to the thinnest available? Then now is the time to tip those valve stems so you don't have to tear it all apart again when you hit the bottom of the shim range.

Remove the pistons and soak them in carb dip for a day or so. This will loosen up the carbon and allow you to remove it, including any that may be down into the ring grooves.

I agree with the others suggesting replacing the rings. Break the glaze with a bottle brush hone first of course.

Oh, and never use green Athena brand gaskets. The base gasket in particular is evil and sure to fail.

Ness, I take it you like them. :lol:
Steve

Why did you have it honed if you plan to re-use the rings? Honing is a surface treatement to provide a surface that new rings will lap into (aka "seating the rings") You only have half the equation with the old rings. If you spent the money to have it honed you should put new rings in too. The bike may or may not need a valve job, but valve seals are almost mandatory. The cost is so small compared to headache they can cause down the road. Many auto parts stores will loan you a spring compresor if you need one.