my brothers quad is like that could be that the pilot jet is too small, that your idle is too low or that your plug is bad most likely it is jetting or your carb though give the carb a thorough cleaning, check your fuel lines check your float which might be too high as said before. i tried everything on my brothers quad before i found out the plug was bad. its all about trial and error.
Current Project:1978 Pontiac Phoenix 355 v8
Past Bikes: 1999 Yamaha Big bear 350, 1981 Yamaha XS 400, 1996 Yamaha yz250 1984 Honda big red, 2004 Xtreme cr107, 1999 Yamaha bear tracker, 1999 Suzuki ds80 STOLEN, 2005 Kawasaki klx110, 1986 Honda trx200sx
Daily Driver: 1990 Buick Electra Park Avenue 3.8 v6