Piston Head Black?

[BradZ]

Hey all, after FINALLY removing thhe cooling head, i noticed that the top of the piston is black? And so is the glow plug around it.. Why?

 

[Cyclop3000]

Might be the fuel tinting it, what color fuel do you use? Mine was blue-green when I took my engine apart, and I had ran orange and blue fuel in the rig.

 

[BradZ]

Fuel is a darkish green.
Had a lot of percentage changes also.
Bloody hobby shop....

 

[Cyclop3000]

Yeah I read you...my LHS also does this. Dunk the parts in denatured alcohol or in fuel for a while, you might be able to get the residue off. If not I don't think it's a big problem, I would just run it like that.

 

[olds97_lss]

Over time, carbon/residue builds up on the piston surface. You can clean it off using a rag and some DA. Do not grind, sand or use any abrasive material to clean it.

Sounds like it was ran a bit on the rich side, which isn't a bad thing.

 

[BradZ]

Thats interesting considering after having serious tuning issues it turned out it was running lean. I'm not worried about it, just curious.

 

[Thunder_tiger_eb4]

This may sound odd, but soak the piston and head for an hour or so in a solution of dish washing/ cleaning fluid and polish with a dry lint free soft cloth (an old cut up t-shirt works well!). This trick works for me every time, just be sure to put some after run oil or wd40 down the block when finished and before running rotate the crank whilst spraying a little more wd40 into the block through the glow plug port & carb intake. It will help re-lube the piston & liner and help dispel moisture from the engine, not to mention add lube to the bearings.

As olds97_lss said, it's carbon residue from the combustion process, mainly from running rich, also known as getting "coked up" in the motor vehicle trade. Better to clean periodically as in my own experience it doesn't help good combustion and can play on tuning, not by much, but enough to never quiet get that balance you want/need.

 

[BradZ]

I have no idea how to pull the whole mill apart!
I just took the cooling head off to have a peek!

 

[Thunder_tiger_eb4]

If intending to clean the piston, you need to take it out, which involves taking the backplate off the engine (as well as the pull starter) and also removing the piston liner, not a job for a newbie or the inexperienced.

 

[RC Addict]

Back in the days of carburetors on 1:1 cars we would dribble water into the carb while running to loosen some of the carbon. Too bad it won't work on a RC...

 

[Thunder_tiger_eb4]

Back in the days of carburetors on 1:1 cars we would dribble water into the carb while running to loosen some of the carbon. Too bad it won't work on a RC...

You could just use a drop of petrol i suppose to loosen /soften it up, then wipe round with a cotton earbud. but the head would be easy enough to soak.

 

[olds97_lss]

Back in the days of carburetors on 1:1 cars we would dribble water into the carb while running to loosen some of the carbon. Too bad it won't work on a RC...

Yeah, while running it at a decent RPM. Can't imagine that would be good on a rig with a catalytic converter... We used to do it as well on our pre-cat vehicles.