TOPIC:

When I rebuilt the VM24SS carbs on my 1977 KZ650B I used the rebuild kit from one of the on-line vendors. The kit contained gaskets, O rings, starter jet, needle screw, air bleed pipe, and a choice of main jets and jet needles. One jet was not included which sits top of the starter jet. I reused the one that was in the original setup. My Kawasaki Motorcycle Shop Manual does not illustrate this jet in photos or diagrams, and does not mention it in text. The photos show the starter jet installed down a tube beside the main jet. My carbs are threaded to the top of this tube, with a larger diameter thread to accommodate the 'unknown' jet. I have attached photos of the jet, and the carbs with the jet removed and installed.

Is it possible the tube portion of the jet is broken off. The below photo is the pilot jet your carbs should have.

Photo pulled from Partzilla

Possibly a pilot jet. see #36 in the diagram below.

PILOT JET,#A50
92064-1019

www.partzilla.com/catalog/kawasaki/motor...-b1/carburetor-parts

The vm24ss and vm22ss carbs that came stock on some of the kz650s did have this 50 jet over (or under dependent upon the view) the pilot jet. These carbs have a pilot screw and not an air screw. Not sure why this additional jet was added, but can see it as sort of a limiter of how much fuel is allowed to be pulled up by the pilot jet, or to increase the speed at which fuel is pulled up.

I have removed them and noticed no real difference in the carbs operation.

Thank you for your reply. I have had cold start problems since I first rebuilt this shed find. I decided to try to remove these unknown jets as per the manual and had visions of it starting like it should. It didn't even kick after I removed them. So I pulled the carbs again and put the unknown jets back with the starter jets. It will start, but with a technique that involves stuffing a rag in the breather tube, tickling the fuel line to ensure there are no air locks, saying special words and holding my mouth in a certain way. I then need to baby it along by giving it more air by removing the rag in stages. It will not start on choke, but I can use choke after it starts.
I find it frustrating that there are variations of the same carb and various names for the same parts. So I really appreciate knowing that the 'unknown' jet is a uncommon part, and perhaps unnecessary as I hoped. I'll try removing it again and will rebuild my choke plungers over the winter, although the O rings and dust seals look fine. This rebuild has been going on for 5 years and the bike looks great - I'll post a photo some time. But the starting problems make it untrustworthy to go even modest distances from home. But I am patient and pretty good at removing and installing carbs. thanks again. Robert NB Canada

Yes the kz650s are rather cold blooded on cold starts. But once up to temp they should start without issues. Starting procedure cold should be as follows:

turn petcock to on
pull up choke
pull in clutch
hit starter button but do not move throttle grip
Allow it to warm up and decrease choke to keep rpms down

Without the air filter installed the fuel/air is going to be very lean.

I must be the luckiest guy to ever own a bike. I've owned my 1977 KZ650-C1 since it was new, more than 62,000 miles ago, and I have never had a problem starting it. I've also never removed or changed any of the jets or other metal parts in the carbs, and everything is stock including the airbox & filter. I wonder if the difficulty in starting the bike in question is because things inside the carbs have been fiddled with or the airbox / filter have been removed or maybe the battery is shot? Ed

Yes, the starting procedure should be as was stated - but in this case it does not work. The unorthodox procedure I use is the only way I have found after many attempts to find a consistent way of starting.
Like 650ed, I purchased my first KZ650 new in 1978. I put on 90,000 kms over the 12 years I owned it and it was bullet proof - never stranded me or refused to start. This current bike was a retirement project and was poorly 'stored' for 30 years. I've really enjoyed the project although I'm restricted to working on it by seasons, small farm, wood working projects, etc. .
The rag in the breather tube does not require removing the air filter. It is an 'old school' method to provide choke when the normal system won't work. With tractors you can sometimes soak the rag in gas, but I don't recommend that for non-industrial equipment.
The project bike has original breather box, new carb holders, new air tubes between the breather box and carbs. The battery is new and the bike turns over as fast as expected.
I appreciate the suggestions and questions. I'm going to rebuild the choke plungers over the winter I'm not convinced that is a problem but there is obviously a choke issue somewhere. Thanks everyone.

Have you preformed all the other maintenance procedures. AKA valve adjustment, points adjustment, timing? Is there good voltage to the coils? What condition are the spark plugs? How old is the Air Filter. Might there critter nests somewhere you haven't found yet. You might have more then a carburetor issue.