KZ650 Idle Problems

When I start my bike, full choke then bring it down as it warms up. Once the motor is warm, while idling it will drop then go back up.. Also, how many turns from all the way in should I have the main jet screw adjusted on the bottom of the carbs? Would this be part of my idling problem? Do iI adjust the float inside the carbs by bending the tabs? Just want to get my Baby running right. Any advise will be greatly appreciated!

Sounds like you might need to clean the carbs and blow through the passages with compressed air. Make sure the fuel valve under the carb floats is unobstructed. To set the fuel heights you need to bend the tangs on the float and then once back on the bike you need to check your fuel levels using the clear tube test. You should also spray carb cleaner around the intake boots to check for vacuum leaks. Set the idle as low as it will go without stalling. If spraying the boots causes a change in idle, you have a vacuum leak

BIKEMECHANIC73 wrote: When I start my bike, full choke then bring it down as it warms up. Once the motor is warm, while idling it will drop then go back up.. Also, how many turns from all the way in should I have the main jet screw adjusted on the bottom of the carbs? Would this be part of my idling problem? Do iI adjust the float inside the carbs by bending the tabs? Just want to get my Baby running right. Any advise will be greatly appreciated!

Bending float tabs, playing with main jets, and fiddling with other carb pieces is a REALLY BAD IDEA unless you have first done proper diagnostics to determine the exact cause of your idling problem. The main jet is not at all involved in idling; I wouldn't touch it. Also, leave the float valve tabs alone unless you have done a clear tube test and determined that your FUEL level is not correct. Otherwise you will only cause additional headaches.

I would urge you to get a copy of the Kawasaki Service Manual before you start fiddling with the carbs. You need to use it to develop a thorough understanding of them before you make any changes to them. Otherwise you will un-adjust what is currently properly adjusted. These carbs cannot be tuned using pot luck.

Your idling problem sounds like leaky carb holders (the pieces between the carbs and cylinder head). Here's how to test them:

First - make sure the vacuum caps are tight on the carb holder nipples.

Temporarily set the idle as low as possible without stalling the engine. It should be down below 1000 rpm. The lower the better because when it is set low the carb slides are closed (or nearly closed) and this raises the vacuum level in the carb holders. The combination of the increased carb holder vacuum level and the very low idle amplifies the effect of the leak test.

Once the idle is set low, spray carb cleaner around each of the carb holders where they bolt to the cylinder head and where the carbs attach to them. If there are leaks, the vacuum in the carb holders will suck the carb cleaner in and this will affect the idle. It may even cause the engine to stall. If there is any effect at all on the idle, they are leaking. If the leaks are at the carb holder / cylinder head mating surface you need to replace the holders. If the leak is where the carbs attach to the holders you may be able to tighten the clamps enough to seal the leak. Some folks use starter fluid or other substances for the test, but carb cleaner works best as it doesn’t evaporate too quickly like ether and leaves no residue on the engine like WD40.

If you do need new holders just bite the bullet and buy them. Trying to seal things up with some kind of sealant or goop will only lead to frustration as it will at best only last a short time. Ed

I gotta tell you, this is AWESOME! Thanks so much Ed & Nick!! Leak was at carb side of the holders. unscrewed clamps, made sure carbs were all the way in holders & clamps were tight. Problem solved!