Hey ,for all of you !!!! I am from Portugal and have wr 400 (00) . Ok, i only ried sunday mornings with the gays and i am having the fallowing problem, the bike starts great and for a few miles it runs great to(clean acceleration in all rpm and throttle range) but when the engine starts to warms up it bigins to backfire and it feels like it´s going to stall after 1/2 throttle but if i keep riding it only up to 1/3 of throttle comes up to be ok again(clean acceleration in all rpm and throttle range) doring the rest of the ride if i give it throttle to fast at low rpm it does the same thing again ,then again if i keep ridin only up to 1/3 of throttle for a while it will be ok again. Carb. and ingene have all original parts (eccept for exaust pipe), settings are acording to specification book. If any of you cold help i would apriciate Thanks and sory about the inglis!!!!!