Carbon build up on piston

[huskyohilux]

I just saw this link in another thread: http://www.cpcracing.com/site/256083/page/196309

There

Edited June 13, 2008 by huskyohilux

[Bansh-eman]

over prolonged periods your going to get carbon buildup regaurdless of if your jetted spot on or not just for the simple fact that your running a premix. But if you have an excess amount of carbon built up over a short time span it's becasue your running rich.

[huskyohilux]

I just saw this link in another thread: http://www.cpcracing.com/site/256083/page/196309

There

[Bansh-eman]

Read it again and saw that the check-up should be after 2 hours of riding...I guess after that all pistons get black all over and no fuel could was that off...and my pistons had way more than that on them

what is your mixture?

[huskyohilux]

what is your mixture?

In the early days of them pistons I ran 1:20 but after joining the HQ and reading some, I

[mopar1rules]

i don't know about the 2 hrs run time thing. when i had my shee jetted rich, with 350 mains and 27.5 pilots and 50:1 ratio, i had a carbon circle (about half the size of the diameter of the piston), right in the middle of the piston crown. the rest of the piston, all the way around, was washed clean. it made sense, cause with the larger jets, i had more fuel passing through to wash the oil off the piston tops. i had way more than 2 hrs of run time on it and the piston top still continued to stay "washed" clean, from the extra fuel. but now i also started to think about what Bansh-eman was saying about having the piston tops get black regaurdless, due to running premix (oil & gas are mixed in gas tank, and passing through the same jets). i would be starting to think that the wash clean means rich theory, only works in oil injected (right into crankcase) environments. but then again, i was seeing the same results as the photo, even in my premix environment, so it seems to me that i goes both ways. now it also got me thinking about the rich condition/carbon buildup condition, that you speak of. when running a ratio of lets say 32:1, there should be more carbon on the piston top, then with say a 50:1 ratio, reguardless of jet size. that would be cause less fuel and more oil (in 32:1 ratio), are being passed through the jets. now i just relized something too...i think we (Bansh-eman & me) are talking about 2 different "rich" scenarios. when i mean "rich", i'm talking fuel. i think Bansh-eman is talking about oil, when he says "rich". now, going off the last statement, that would make sense why one would see the same results as photo, when changing the premix ratio of the fuel and leaving the jets alone, in a premix situation. because of less fuel and more oil (in 32:1 ratio), are being passed through the jets, versus a 50:1 ratio, where more fuel is being passed through, then oil. in both cases, there is always more fuel being passed then oil, but i think you know what i'm talking about.

[J-Madd]

Some will argue with me, but the black is from fuel more so than the oil. My 4 stroke engines have had as much carbon as my 2 strokes on gas. On alky,.you run even more oil, but still don't have the carbon build up: thus ruling out oil as the major contributor, imo.