My bike was running great until a few months ago. Even now it runs good just fouls plugs. Since it started fouling plugs i ported the intake boots, very minor porting in the intake and exhaust and removed air box cover completely(had a big hole in it), and a new pro flow foam filter. I was running the dynojet jet kit with 150,148 jets. I have the curtis sparks pipe with no spark arrestor.
Tonight i just changed down to 144,146 and it didnt feel as good but plug looked better. A friend told me something about a throttle positioning sensor on the side of the carb bu i see no such thing in my service manual. I am will check out the air screws tomorrow didnt look at them to see if they were clogged yet.
Thanks Rudy

 

I fouled a plug this season... first one ever on a 4 stroke, but I am thinking it just plain went bad.. anyhow what does yours do when the plug fouls? Are you running any kind of octane boost or fuel additive?

 

I would go back to your old jets or 146/148 and a hotter plug.

 

No octane boost just 92 octane, Who sells a hotter plug or who make one.
Rudy

 

bosch platinum 4 prong. They are the coolest looking/hottest plug I know of. Most likley wont foul that thing out!

-nick

 

scoots just don't go fouling plugs for no reason---ya propably got something in your pilot jet circuit---acts just like having the choke on--clean the carb and set your low speed screws by the tech report yamaha has out---most of these scoots are a tad bit lean on the bottom end

 

think i found the problem. That thing my friend told me was the choke cable. I pulled it out and the spring was disenegrated, nothing left. Must have been like riding with the choke on. Just put my old jets 148 and 150 dynojet and made a pass down the street. I think i might even be running lean now. Anyone know where to get a 152 dynojet from. Will call dynojet tomorrow.
Rudy