how to tell if its lean

[Fireroad Express]

NO NO No hold it wide open, kill it then take out the plug then look through the plug hole with a light and a lil magnifying glass and you can tell if it is lean by how big the wet spot of gas on the piston...the smaller the wet spot the leaner it is. well that s how you fine fine tune the thing

 

checking "piston wash" is actually a real good way to check your air/fuel mixture on a two stroke engine where you can see directly down the plug hole. you are checking the size of the carbon deposit on the top of the piston. the bigger the deposit the richer the the mixture.

[fishwater]

Exactly on snowmobiles you look down the plug hole to see piston wash but on a bike I would just get it warmed up & do the WOT test. I wouldn't waste any time chopping a plug.

[phreak]

checking "piston wash" is actually a real good way to check your air/fuel mixture on a two stroke engine where you can see directly down the plug hole. you are checking the size of the carbon deposit on the top of the piston. the bigger the deposit the richer the the mixture.

i think you have that backwards.

 

[dajogejr]

i think you have that backwards.

 

 

Try that with a methanol bike....there should be little to no coloring, no deposits...

Methanol blows out the exhaust whatever it doesn't burn...

[fishwater]

The thought is that if it is too rich it will wash the piston & leave it clean looking. When tuning sleds I always made sure the piston wash was minimal & the burn pattern looked good. You get a feel for it based on conditions & the way the sled runs in addition to the piston wash.

[Snopczynski]

That center one is what my stock pistons looked like when I tore mine apart to do my port job last winter.