Has anyone on here fitted a bst40 Mikuni (mine came from a Ducati 640) to a xr600r only I need some help. I fitted the Mikuni because with my standard Keihin carb the bike takes too much kicking to start it, I've stripped and renewed jets, gaskets, 'o' rings etc. but with no success. The good news is it starts second kick if not firs kick every time, the problem is it seems to run poorly above 1/3 throttle, its like its starved of fuel just like when you know you have to switch to reserve on the fuel tap. I should also say that I've been in conversation with motolab on this forum and shown him photos of the internals of the carb and it checks out ok. The original owner swapped for fcr carb and the Mikuni was working fine on his bike prior to removal . The fitted jet sizes are :- Idle 45 Main 152.5 Please feel free to comment all help gratefully accepted.