ok, i have a 1985 yamaha yz250, i got it like 3 months ago nd it ran good but it wasnt jetted right, i got it from someone up in the black hills of south dakota, and now i have it in the plains of southdakota near minnesota...FLANDREAU SOUTH DAKOTA...anyways im not sure what jetting to use for my bike, im not in as high of an altitude as it was be4. nd i am fouling spark plugs like crazy, i believe i have a 290 in right now, can anyone tell me what jetting to use