Piston color..... lean, rich, ????

[cals400ex]

when looking at your piston, what color usually indicates you were running the bike too lean and rich? i realize that when you shut the bike off you might not have been using the mainjet throttle position so you might not be getting exact readings. however in general, what color indicates lean and rich?

[pairanutz]

do you mean plug color-most people check their spark plug not their piston
black is rich
white is lean
light tanish is ideal

[zephead400ex]

Originally posted by pairanutz
do you mean plug color-most people check their spark plug not their piston
black is rich
white is lean
light tanish is ideal

No, he means pistin. Cal knows about plug readings.

[cals400ex]

yeah, i am referring to the piston. i was just kind of curious since i just took my 406 apart and am installing a 426 here shortly. i only have about 8 tanks of gas thru the 406 but i needed something to do now that summer was here. so, i will put in a 426. :D

[cals400ex]

plug reading......... whats that??????? :eek:

[ghak99]

Originally posted by cals400ex
plug reading......... whats that??????? :eek:


LMAO...I believe it is still the same as far as black= rich, white=lean, but I have never seen a brown/tan piston...:confused:

[hondarider2006]

Originally posted by cals400ex
plug reading......... whats that??????? :eek:


There are little words on the plug that tell you if its running lean or rich......:o









About the color of the piston....I would think it would be about the same as the plug. If its all black, than your running rich. I know when me and a friend tore apart his snowmachine motor, his pistons has some black carbon build up on the top of the piston b/c he had it running really rich. I would think a tannish color is what your looking for.

[cals400ex]

yeah, i really don't know. my piston had a little bit of brown on it but it was mainly black. i know more carbon build up may be on the top of the piston so i didn't know if that would mask the true color or not??

[sparks400]

ive only seen black pistons, from the carbon build up

[UglyMotha™]

you don't read a piston like you can a plug so quit trying to compare the two, carbon buildup is bout all your going to see, the richer it is the more of a carbon build up you'll have

[KASCHAK]

my stock piston is the alunimun color or whatever and were the exhause valces were its black.

[KASCHAK]

i will add that i had perfect jetting.

[KY Woods Rider]

You really can't tell that much about your jetting by looking at the piston, or at least I can't. Maybe someone who sees a great deal of used pistons and knows the jetting that was used and the conditions they were run in could tell, but I can't do it. Of course you can tell if you're way off, but you won't be able to jet your quad based on what you see.

Basically, there is going to be one color, and that's the usual black carbon color. If the motor has been run more than a couple hours, there's going to be carbon on there if everything is okay. That's just the way it is, because unless you're jetted too lean, the temps on the piston dome shouldn't be getting high enough to burn off all the carbon. Going by the amount of carbon can give you some indication of the jetting though. A thin layer of carbon is normal. If you basically don't have any carbon at all, you're too lean, and if there's a thick layer of carbon that you can chip off in small chunks with you're fingernail, then you're too rich. However, keep in mind that the amount of carbon on the piston will not only depend on the jetting, but it will also depend on how the motor was run and whether or not there was oil making its way into the combustion chamber.