How much carbon on the top of a piston is "acceptable"?

DRZ

DRZ

DRZ

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Finally managed to get the head off the engine (will update the other thread accordingly) but the first thing that struck me was the amount of carbon buildup everywhere. Obviously, I was expecting there to be some, but the top of the piston had carbon to a depth of over 1mm and the valves werent far off either.

I wasnt expecting that much, so is that normal?

Its a 124cc single-cylinder engine, not sure how many miles its done since it was last looked at (if ever) but there is 10k miles on it in total.
 
My rotors were pretty badly covered in carbon when I did my rebuild, nearly 1mm in places.

When I started cleaning them it was flaking off in chunks....
 
Enfield said:
It certainly won't hurt to clean the head up mate that's for sure. :)
Click to expand...

Oh I fully intend to, hence why its off :D

I was just wondering if this much carbon was an indication that something was WAY off? It hasnt been lunching on spark plugs recently but then it hasnt been running sweetly either...
 
Carbon on the pistons/other related engine internals is generally a sign of oil getting into the combustion chamber or overly rich fuel mixture. It can also be attributed to impurities/additives in the petrol.

In Drex's case it most likely had something to do with something off on his turbo. (guessing here)
 
I would say that if there is more carbon on one piston than any other (like a lot more) than that could indicate a problem somewhere.

When you bolt it all back together I suggest getting some of that carb cleaner spray (safe for cars with cats), and spray the stuff directly into the throttle body with the engine on and revving. This should clear out some rubbish... :)
 
Mickey_D said:
In Drex's case it most likely had something to do with something off on his turbo. (guessing here)
Click to expand...

I'm sure it was because it was running massively rich, it was running so rich it was choking it at the top-end causing a huge missfire at 7k and above (with corresponding black/dark brown smoke).

That was with the old F-Con V piggyback ECU that was on there, mapped by a Chimp I think :rolleyes:

The Apexi Power FC cured that ;)
 
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