rpms racing

Today I installed my carbs back on my 80 KZ750 LTD . I cleaned the carbs and installed new kits. Floats are at 4 mm precisely. I do not feel it is out of synch. If I am correct in assuming yellow paint on the synch screws is from factory, the only screw that has been messed with by PO is the middle. Races when the throttle cable is not even hooked up.

So basically, when I start it, it immediately races up to 4-5k rpm. Any ideas? Thanks.

Do you have the choke on? It will race at high rpm's with the choke, but they should fall when the choke is closed. You may have an air leak some where, spray wd-40 around the carb boots and if the rpm's drop you found your leak. The screw in the middle controls your idle, if you turn it one way or another does it affect the rpm's?

have you turned the idle speed screw out?

assuming you did it, then most likely they are out of sync. check also that you dont have air leaking in form anywhere

Turned the idle screw all the way to the left and right, does not seem to make a difference.

I wouldnt think they are out of synch, all the butterflys look pretty close. Is it possible I did not clean a passageway enough?

And I messed with the choke open and closed, it doesn't make a difference.

Sounds like a vacuum leak.

I agree on the vacuum leak, I would pull the carb holders off and reattach them using some fuel approved gasket sealer. If the problem still occurs I would use some propane or something around them to see if their is still a leak.

What exactly do you mean by the carb holders?

ravenz07 wrote: What exactly do you mean by the carb holders?

The rubber holders that bolt to the block and the carbs mount to them will be the carb holders. They will dryrot in time and create leaks that can not be seen with your eye. That is where the wd40, carb cleaner and such come into play. When sprayed on the leak it will suck in the aerosol instead of air and the idle will be affected by the richer mixture for a split second.

"Races when the throttle cable is not even hooked up"

In addition to the above suggestions check the operation of the mechanism which the throttle cable connect into. Pull it back and let it go. it should snap right back. Might be something jamming the operation,

good luck

Not unusual during idle and running sync adjustment for the throttle slides to need lowering from their positions as set during bench sync.

Failure to have idle thumbscrew properly positioned during bench sync may cause inability to sufficiently lower slides to reduce idle rpm.

Perhaps the thumb screw has lost contact with carb puller assembly (bell crank) leaving slides stranded in their "too high" bench sync positions.

In such event, a repeat bench sync is needed, with attention to the idle thumb screw position before equalizing the slide heights.

Good Fortune!

EDIT -- this would apply to manual slide carbs, and NOT to the stock CV carbs on 1980 KZ750 4 cyl.

ah, I always knew them as intake boots. They seem to be in good condition, getting the carbs off and on is no problem. The seem to be still soft and without cracks, but I will further inspect them tomorrow.

Will any pics help to figure it out? What would need pics of?