Problem with over reving.....help needed!!!

[Bealz]

I have put the motor back into the zzr after doing the valve adjustment as I need to get back to work. I have a problem with over reving and I've tried everthing to fix it and it wont go away. I will try to explain it as best I can.

when I start the bike, I have got it to idol ok but any movement on the throttle and the rev's atart to climb to about 4.5 - 5 thou quite rapidly and sit there. I have to turn the idol screw down to bring the rev's down until they reach 1.5 thou and then turn it back up slowly before it stalls to keep it at 1.5thou.

I have pulled carby's apart and checked everything, main jets are clean and not blocked, diaphrams are clean and in good condition, the black slids inside the carby's are running up and down smoothly, pilot screws are 2.5 turns out, floats are at 17mm closed, throttle cables are free moving and adjusted correctly, rubber carby holders are tight on both ends, butterflys inside carby's are opening together and are returning to closed position.

I have done all of the above to another set of carby's from a gpx and fitted them to the bike and still get the same problem. Is there something I'm missing or have not checked, the fact that the idol screw has to be adjusted to bring the rev's down makes me think its the carbys.

Is there another reason the bike would rev so high and get stuck there, something mechanical maybe, I have replaced the airbox with pods so air is not a problem, I can not think of anything else that would cause this problem

[Desmo]

Throttle return spring?

[Bealz]

throttle returns to off position I even forced it backward and it still revs

[smeghead]

Air leak between the carbs & the motor; either the manifolds themselves or gasket prob.

If you take the plugs out do they differ in colour/condition? If they do then it may point the carb/intake that is giving the prob.

If you can look at the carb mouths when the throttle is moved do any of the slides move more than the others?

[Skut]

Ahh Smeghead, you are scarily smart and helpful

[Bealz]

spoke to Andrew today from TWW and he suggested unscrewing pilot screws 3 - 3.5 turns instead of the workshop manual setting of 2.5 turns and solved my problem. bike was running to lean.

[chee]

i would have guessed an airleak.

[Bealz]

yeah he mentioned air leak as well

[ranmar850]

Changing stock airbox for pods could do this, particularly if old filter in airbox was neglected, and idle mixture adjustments had been made ever-leaner over the years to compensate.