engine overhauld, new valves installed, grinded, adjusted, everything.

Carburators disassembled/assembled, cleaned, iddle speed adjusted, synchronisation adjusted, everything.

problem:

Engine starts/runs on choke, to warm up, when i push back te choke, the engine runs for a little while on normal iddle speed [1000-1300 rpm] and then suddenly refs up to 3500-4000 rpm -for a little while-, but drops back again to iddle speed.

After operation of throttle, the refs again raise, and drop very slowly after little while, but then again, engine reffs up again to 3500-4000 rpm.

WTF could be the problem ???

 

sounds like the carbs arent sync right.. had that happen to zx7

 

Carbs out of sync or maybe drawing air at one or more of the intakes. Get it to idle and shoot some carb cleaner on the rubber intake boots. If the Rpms suddenly change, you have an air leak.