I've done a search on fouled plugs and read the posts, but none seem to address my issue...maybe I'm dense. Anyhow, here's what's going on. I have an 02 YZ250 that I bought new. Until several months ago, I never fouled any plugs. Currently, every ride costs me a new plug. I start the bike, close the choke immediately, sometimes I idle it gently on the stand, other times I ride very easily until the engine warms up. Either way, after about two-five minutes the plug will foul. By now the engine is somewhat warm, I put in a new plug and the bike runs fine the rest of the day. Unless of course, it's allowed to completely cool, then it'll foul again.
I've not changed the jetting & I ride at the same locations all year round never with any problems -- until recently. The other posts suggest changing the jetting, but it's always been fine. If it were dirt, then it would foul throughout the day, not just in the first few minutes. If it were the float height it'd foul all day also, same with reeds.
The plug that fouls during the first couple minutes is black and oily. After riding all day, I look at the plug and it's half mocha colored and half black. By half and half I mean if you were to look straight down at the plug, from 9:00 to 3:00 it's mocha, from 3:00 to 9:00 it's oily black.
I'm perplexed.
I've not changed the jetting & I ride at the same locations all year round never with any problems -- until recently. The other posts suggest changing the jetting, but it's always been fine. If it were dirt, then it would foul throughout the day, not just in the first few minutes. If it were the float height it'd foul all day also, same with reeds.
The plug that fouls during the first couple minutes is black and oily. After riding all day, I look at the plug and it's half mocha colored and half black. By half and half I mean if you were to look straight down at the plug, from 9:00 to 3:00 it's mocha, from 3:00 to 9:00 it's oily black.
I'm perplexed.