Running to Lean

[mtscott]

Has anyone damaged their engine by running too lean on the jetting? I have guy at work that blew up his KX250 doing this. How would you know if you just jetted your bike too lean??? Just paranoid about blowing it up is all!

YZ450F 2006

[642MX]

Stop being paranoid. Remember its a blue bike, not green, yellow or red.

[grayracer513]

Two-strokes are much touchier about this because the oil is carried by the fuel, and if there's too little fuel, there'e too little oil, too.

Lean mixtures tend to elevate combustion chamber temps, and can raise them to the point that preignition sets in, but the engine usually shows symptoms of poor performance before that happens.

[stock510]

Has anyone damaged their engine by running too lean on the jetting? I have guy at work that blew up his KX250 doing this. How would you know if you just jetted your bike too lean??? Just paranoid about blowing it up is all!

YZ450F 2006

You will notice that it pops A LOT on closed throttle, if its bad it may shoot flames. Tends to be hard to start.

http://www.transworldmotocross.com/mx/how_to/article/0,13190,1018579,00.html