I have an 78 dt400. After engines warms up(about 2 min) it starts idling high, then another minute it starts screaming away at like 6000 rpm and higher. Cleaned the carb and checked cable. There fine. Can anyone offer any advice?

I have an 78 dt400. After engines warms up(about 2 min) it starts idling high, then another minute it starts screaming away at like 6000 rpm and higher. Cleaned the carb and checked cable. There fine. Can anyone offer any advice?

hi m8, start ur bike up and get it warm, on the carb there is a screw with a spring on it, undo it slightly until it sounds ok, that should sort it, i had this problem on one of my pit bikes.

yeah my carbs (mikuni round slides) have the throttle idler bolt in between the two middle carbs and hard to reach underneath. tinker with that....

also it could be a induction leak = air leak passed the front of the carb

Ha. Same happened to me with my '77 dt400. The needle in the carb had holes corroded into it letting extra gas into the engine. Sprayed it with paint which sealed the holes. Has been perfect since!