Probably the Carburetors

Things are coming together now. The engine and trans run good, now I'm looking at getting her carbs to to the same.
What's happening is that I can start her up on full choke from a dead cold on the starter for about two seconds and she fires right up. The problems are she won't run off choke no matter how long she has been idling. When I give her some throttle she will die unless I do it really slow then only to 4k. I cleaned the carbs pretty thoroughly, and used replacement kits. I don't remember the jet numbers but I will look them up today, (should be stock). I also need to do the clear tube float test to check them out as well. Any advice would be great!!
Thanks!

Have you disassembled and thoroughly cleaned the carbs? If not, I would do that first - ideally buy rebuild kits so that you can replace the jets. At the very least, you may want to replace the idle jets - they have tiny holes, get clogged very easily and are difficult to clean!

Also, make sure the carbs are pushed all the way into the rubber manifolds to the engine - it is easy not to seat them properly and get an air leak!

Good luck!

Sorry, forgot to mention I did use rebuild kits. I have completely gone through the carbs. When I first started on them there wasn't any gel or bad fuel in them. They sat for 25 years so everything was dust. I have gone through and replaced everything in the rebuild kits-
needles, main jets, pilot jets, float needles.
I have torn down each carb. and cleaned it in a solvent tank, and carb cleaner.

O.K. - then two areas you should check. Float level - you can do this with the clear tubes and float bowl fittings, or there should be a measurement that you can check with the carbs off the bike: Remove the float bowls, invert the carbs and measure the distance from the float to the carb - specs should be in your workshop manual!

Second thing to check for is vacuum leaks - make sure the carbs are into the holders (manifolds). That all vacuum tubes are connected and the balance tubes have good stoppers on them. Also check the manifolds themselves for cracks etc. At 25 years of no use they may be too brittle to seal properly and you may have to buy replacements.

Also check the mechanical sync of the carbs - again, the procedure should be in your manual.

Looks like the jets I am running are 102 and the pilots are 15. I have synced all the carbs. All vacuum lines have new plugs on them I got rid of the emissions lines and capped the exhaust reads. Carbs have been thoroughly cleaned. I took each one completely apart and off of the holder. One question I have now is, what should the needle position be in? When I rebuilt them the old ones where in the third position, so I put the new ones there as well. Another oddity I have found is that sometimes 1 or 4 won't fire, and it changes every time I start her. Or sometimes every piston does fire. I have new coils from a complete dyna electronic ignition and coil kit. Coils have plenty of power too.

The pilot circuit is obstructed and that is why the bike won't run off choke.

From your blurb in your signature, this bike looks like it is a project. Have you checked valve clearances, tensioned the cam chain and how did you adjust the timing? Keep in mind I have no idea what your level of mechanical expertise is so any of things could be a stumbling block to getting the bike to run properly.

The reason I bring this up is that since you synchronized the carburetors and the bike won't run off choke, it makes me wonder about how some of the other things were done... not trying to be critical, just want to be of help. For instance, how did you check coil voltages? Let's get on the same page with some info... I have brought dozens of old bikes back from the grave and when I hit the starter the first time, I am pretty sure that the bike will start an run pretty much spot on. I bet we can get your bike running right if we back up and make sure the other stuff is okay before tearing into the carbs again (as you likely will need to).

I had a machine shop go through the heads, mostly they did a valve job and replaced the valve shims. Clearance is good. I used a adjustable timing light to set the timing. I believe I adjusted the cam tensioner correctly.? I have a good deal of experience with engines from small briggs to big blocks. I am good with electrical and mechanical, done 3 small block rebuilds, always had a problem with carbs though.

I personally would check valve clearances again with the engine all together even though the machine shop checked them. Best not to chance anything.

I get nervous giving carb advice to someone who hasn't yet checked to see if the bike has oil in it. I think I have been guilty of this in past and I think we all jump to come up with answers where we would be better off analyzing the question a bit. You seem to have things under control as far as the mechanical stuff and ignition stuff so perhaps the carbs are the culprit.

The pilot circuit is still gummed up. If the bike will start on choke, it is running on the air/fuel mixture the choke (which is actually an enrichener) gives the bike at idle. You shut off the enrichener and the bike falls on its face. Is the bike driveable? This issue relates to the pilot (aka idle) circuit which affects things to about 1/8 throttle or a bit more. If the bike is driving, does it do the same thing in mid-range or have you not gotten that far. Anyway, I will be offline for a couple days and will likely get back on later this weekend hopefully. If you spray carb cleaner using the little straw they give you, does it come out the diffusion hole on the engine side venturi bottom? If it doesn't you need to keep cleaning. We use an ultrasonic specifically because these internal passageways are tough to clean.

Thanks for the advice George, your tips lead me to find out the rebuild kit I used is not the same as what was in the carbs. The mains were 97.5 and the pilot was (hard to read-510) I don't think it was a 0 but a weird little symbol. Once I cleaned them up and put them back the bike is more responsive now but still won't run off choke. I will take a closer look at the pilot circuit to see if I can clean it out better. Also I did check the valve clearances once the head was together. I am like you I like to check someones work before firing it up. Something that runs up to 10 grand needs to be accurate. This is the first bike I have worked on, the chevy's I worked on only run up to 7 grand
Thanks,

This diagram from Kawasaki.com shows two versions of pilot adjustment screw, one being the side-located pilot air screw, and the other being the bottom located pilot mixture screw.

Am wondering which is applicable in this instance, as the internal pilot circuit passages are different.

[Click on image for larger view]

79 KZ650's only have the side pilot air screw the bottom one, pilot mixture screw is not available. It is simply not bored out for there to be a screw just solid aluminum.

bubbap wrote:

79 KZ650's only have the side pilot air screw the bottom one, pilot mixture screw is not available. It is simply not bored out for there to be a screw just solid aluminum.

Hmmmm ...

In the diagram, #42 is a side-located pilot air screw shown in upper pic, and #30 is a bottom-located pilot mixture screw shown in lower pic.

Good Luck!