i have a 87 lt 250 quad racer it starts first kick idles good revs up good but bogs out and dies after a couple minutes and wont start back up unless it sits for a few minutes like its getting to much fuel it has the stock 32mm mikuni carb fmf pipe 240 main jet not exactly sure whats done to the motor but it has been rebuilt and its not stock im leaving sunday night to go riding and need help asap and i dont no wat screws on the carb of the 2 do what thanks for all your help
chase

 

mine has a 240 but no air box with a real big k&n air filter with outer wears. if you have an air box you may wanna try going down to a 220 main

 

if i were you id run it with the choke on, then after you did that put some small small wire in the main jet, see what it really wants, then figure out what to do.