1984 KZ750L4 (Canada) Idle issue

Hi, l have a 1984 KZ750L4 Canadian model that is completely stock pipes/airbox etc which does not idle when warm (have to hold throttle open) but starts up cold with choke and does idle around 1500 rpm for a few mins.

Currently l have done the following:

Carbs have been ultrasonic cleaned and from the diagrams that l found on this site l have confirmed that there are not blockages in the pilot circuit or starter jet circuit with compressed air, in all the carbs look almost new.

Current carb settings are:
Main jet 110
pilot jet 37.5
needle Y270 (clip in middle)
pilot screw 2 turns out (have tired both in and out 1-1/2 that made no difference).
My altitude is 1600 feet

Valve clearances are within spec and carbs have been balanced. I have also checked the resistance on both coils which is reading 4 ohms and spark looks good, tested for air leaks on all the carb boots with WD40. Any ideas what could be causing this issue? 

Thanks,

If turning the mixture screws three turns each changed nothing, there is a good chance that the problem is there. When you rebuilt the carbs, did you replace all of the orings and gaskets, including the tiny orings on the mixture screws? Are you sure that the mixture screw orings went in first, then the washer, then the spring, and finally the screw?
Did you ensure that each screw’s tip was in tact and not damaged?

Have you tried turning in the throttle stop screw to increase the base idle speed?  And of course, vacuum sync the carbs?

wrote:

If turning the mixture screws three turns each changed nothing, there is a good chance that the problem is there. When you rebuilt the carbs, did you replace all of the orings and gaskets, including the tiny orings on the mixture screws? Are you sure that the mixture screw orings went in first, then the washer, then the spring, and finally the screw?
Did you ensure that each screw’s tip was in tact and not damaged?






 

The previous owner rebuilt the carbs before l started checking/cleaning but he could never get the bike to run right either. All jets and orings/gaskets appear new and there is no damage to the tips of the screw, this is how the they came out there is only a top O-ring on the screw and a spring below, no sign of any washers, missing washers?




ibb.co/cX1v38C

 

Nessism post=860652Have you tried turning in the throttle stop screw to increase the base idle speed?  And of course, vacuum sync the carbs?

Yes l can turn it in while feathering the throttle to keep the engine from stalling until it gets to the point when the RPM hangs at 4k+ after the throttle is feathered

I synced the carbs on the bench using a very thin bit of wire as a gauge and then with the engine running using carb balancing/sync vacuum gauges have confirmed settings are pretty close. Though its hard to make finer adjustments when the engine does not idle when warm.


Edit:

This diagram matches the carbs the bike has apart from the rubber plugs that cover the pilot jet are not shown which l currently have fitted, From other posts on the form there was talk of some later models not needing this rubber plug as the idle jet pulls fuel straight from the bowl rather than the main jet on early models. Though as there is a little hole going from the main jet tower to the pilot jet l assume these carbs that l have need to keep the plugs in place?


www.kawasakipartshouse.com/oemparts/a/ka...162/carburetor-parts