Carb issues

[tmlawr]

1996 Yamaha 350 bigbear
stock air filter and Cobra pipe
new std carb kit, std jetting

Bike ran great for hour or so at higer speeds, but fouled plugs quickly at lower speeds.

pilot jet is 2 - 3/8 out, needle is set in middle (stock), run like crap with a leaner setting and barely runs on a richer setting.

shoud i give the pilot jet a 1/4 turn or so out to stop the lower speeds from fouling?

Could it be my CDI box acting up?

I have replaced the outter coil, with no change in proformance.

i am ready to sink it inour pond!!!

[bwamos]

Have you replaced the main jet?

You have to replace the main jet with a larger main jet when replacing with an aftermarket pipe.

Air Screw. Start it at about 2 turns out. Keep turning it out until the engine runs at the highest RPM.. then turn it back in a 1/4 - 1/2 turn to keep it from idling too hot.

Needle.. most likley need to move the needle up 1 spot from stock (clip down 1 notch)

Since you have stock air filter still.. I'd reccomend moving the Main jet up just 2 sizes. Basically, if you're running a 135 put in a 140 to start with.

Basically an aftermarket pipe makes the system breath better.. therefore you have more air.. and you need more fuel to compensate.

A lean mixture will bog and run like crap. A rich mixture will run ok but spit/sputter a lot. A good mixture will be obvious when you get it.

[tmlawr]

I READ THAT YOU SHOULD GO UP ONE JET SIZE WHEN REPLACING PIPE, BUT A DEALER (NOT A MECHANIC) TOLD ME I DIDN'T HAVE TOO.

BUT WHY DOES THE BIKE RUN LIKE CRAP WHEN I ADJUSTED THE NEEDLE VALVE TO BE RICHER, DOES SEEM TO BURN ALL THE FUEL OFF THE PLUG?