[gpz-750uni]

Hi

I have a gpz750 that I bought about 2 months ago. It ran fine at first, although occasionally took a while to come down from high revs at idle. After a while it started to stall when idling and then get stuck on around 7,000 revs (constantly not jumping about) once the throttle was opened.

I have pulled out the carbs and cleaned out all of the jets etc. Today I put the carbs back in and now it won't start at all! No fuel is coming from the tank even with the tap set to 'prime'. I think it may be a vacuum leak - any ideas? I've also checked the exhaust system for leaks and there aren't any. Also the previous owner but a ZX-6R Ninja exhaust on it, would this make it run too lean?

Thanks

 

[JimmyD]

If the petcock is set to prime and nothing is coming out then you have something blocking the petcock. Prime = unrestricted flow.

Drain the gas, take the petcock out of the tank and disassemble. I imagine your tank has crap in it. Use an inline fuel filter.

 

[gpzrider]

JimmyD is 100%. Vacuum will only be effected in the run and reserve positions. Prime should free flow due to gravity alone. The tank design on the GPz leaves the back corners in the perfect position to collect crap and rust out. While you have the tank off and the petcock out is the perfect time to clean and seal the tank if you see any signs of rust.

As far as the hanging throttle, check your rubber boots for cracks and loose connections and make sure the idle isn't set just a tad too high once it's up and running again. That will cause the engine to be slow in coming down in revs. The manual also tells you to install the clamps on the junction of the carbs to boots with one clamp upside down of the other three. This is important for a reason, that clamp will interfer with the throttle linkage causing the throttle to remain open. Trust me, learned that one the hard way.

 

[onkelb]

You might also want to check the vent passage in your tank cap. If the vent passage is blocked it will create a vacuum in your tank that will prevent fuel flow - other than that I agree with JimmyD.