FZRSupport: the FZROnline Archive

Once warm the idle will spontaneously raise to around 1600 and fall back down to 1100 at random.

Almost invariably an air leak on the intake side.

Always check the easy stuff first. Make sure your throttle cables have the requires play to allow the carbies to return to the stop screw.
To check for an air leak;
1) First a visual inspection for cracks and loose clamps.
2) Setup up the bike so you can run the engine with the fuel tank removed (you want access to the carbies).
While idling spray something like WD40 or even water around the carby boot joints and watch for a change in revs.

Thanks. Man I hate pulling all the stuff off to get to the carbs....my next bike will be fuel injected.

Sounds like the problem i have been trouble shooting; WHICH i pinpointed last night...

For me... The same thing would happen... while Riding sometimes i would idle ok, and other times i'd get to a stop light and it would NOT idle below 2,500rpm.

Ok, to the point... My Intake Boots all have cracks in them; these cracks allow unregulated air into the engine causing it to run lean which increases the RPMs. To test this i removed/put the gas tank on a stool next to my bike; started the bike, and sprayed Starter Fluid around the boots... Within seconds the RPMs shot up and the exhaust popped a little indicating the boots are in fact leaking.

** Setting the idle screw to lower RPMs makes it so the engine isn't getting enough air to maintain idle; but when you increase it slightly the extra vacuum pulls extra air through the cracks and the RPMs spike higher than you want.

Check your boots for cracks using the method i just described.

Brand New Boots can be found on Ebay for under $100.00 --don't try to repair them, it wont really work.. Believe me i thought about it.. Too Much Air will make your engine run lean, which can and will destroy it..

Let us know what you find out.

-Pete