- Oct 29, 2002
Fouled 4 or 5 plugs on my 2003 YZ250 this summer, normally at start-up or shortly afterwards. Choke is turned off as soon as possible after she fires, and it still has fouled. If I get passed start-up, she runs w/o fouling for the remainder of the day. Factory calls for 1 turn out with the standard 50? pilot jet, and I've been running mostly at 1 - 1.5 turns out on air screw. I'm at 900 ft. elevation and most of the riding has been above 70 degs. F. Also experiencing lots of spooge from the power valve chamber vent line. I recently ran at 2 turns out and it appeared to clean up the exhaust smoke, and ran well. Other than this fouling, the bike is fantastic, and it's supposed to have the best carburetion out there according to the magazines. Anyone with similar experiences ?. The bike is stock. I'm not sure whether to open the air screw further (> 2 turns), or go with the next smaller pilot jet.