chachi

What is causing a layer of black/dark-brown deposit to form on my piston and button? Is it from running stale or bad fuel? Or is it from running my engine out of tune? The only substance that seems capable of removing the deposit is gentle polish. Engine cleaner won't.

afm

It's carbon deposits from the oil than burns off the fuel during combustion. Depends on fuel you are using, but mainly because of over rich mixture. Now, all fuels leave that layer over a long period of running, that's why I clean them after every 3 races, but if you're getting those layers after one run, your engine is tuned to rich.
AFM

BrainTeased

iTrader: (4)

That was very helpful afm! thank you!
Also i would like to ask a question concerning the black deposits!
Would the same thing apply if you treat your engine with after run oil after the weekend?

chachi

I have been running fresh fuel and the nasty deposit is gone. Now the piston and button have brown/tan coloured residue on them but none of nasty tar black deposit.

TAW

iTrader: (18)

So what is recommended to clean the piston with?

stradith

Jay, its samson...call me and I'll tell you exactly why your engine is acting the way it is.

you know my number...don't for get AFTER 6PM!!!!!...hahaha...

Later dude,

The Vampire

stradith

A good cream to polish the bottom of the button and the piston is a stuff called Metapolish. It comes in a tube, the same size as tooth paste and can be found at auto detailing stores and/or hardware stores. It is generally used for polishing rims and anything metal. Make sure you don't polish the side of the piston and inside the sleeve as you know that polishing is a form of grinding...so compression would be reduced. Clean it off with motor spary after you polish. You can also use this to polish the crank in certain places and the exhaust outlet.

Hope this helps.

chachi

Ah! The Crackers are taking over!