I have a carb question . I’ve been working on a friends Losi 5t 2.0 . It has a 1107 Walbro carb with the bearing . This is his third carb . That i had to install for him . For some strange reason .. he leaves my house with it running great . Then comes back with it not being able to idle . I zero out the throttle servo and set the brakes and throttle arm . I have 6 cars running 1107 and 1257 with no issues . But his car starts off great thing comes back messed up . Can someone give me an idea of what can be the problem please . 