'79 KZ650C misses/backfires

Thanks baldy. I'll have to double check the petcock to be sure.

Manual petcock typically has two equal size fuel outlet nipples and no other nipple. Settings of ON, OFF and RES (reserve).

Vacuum petcock typically has one or two equal size fuel outlet nipples and a smaller vacuum nipple for a vacuum tube from carb. Settings of ON, RES and PRI (prime).

Good Luck!

As and when parts are needed, Z1E is an excellent source with very reasonable prices and best service on the planet.

For a sample, click here > Airbox hoses

Good Luck!

I've cleaned the(Mikuni)carbs and have run into another issue. On the rim of the bowl inside, there is a clip holding a ball bearing and a round brass piece. What purpose does this have ? I'm asking because I found that one carb was missing the clip and bearing.
BTW, the petcock seems to be a vacuum type(on,res,pri). I now have to figure out why and what else has been plugged. Could this cause or be part of my original problem ? The carbs were actually not that dirty.

On the rim of the bowl inside, there is a clip holding a ball bearing and a round brass piece. What purpose does this have ? I'm asking because I found that one carb was missing the clip and bearing.

If it's the #2 carb, then those pieces are part of the accelerator pump circuit. It is an outlet check valve for the accel pump. I'm not sure if ALL the carbs on the rack use that same setup since my C2 (1978) doesn't have an accel pump. The FSM shows it only on the #2 carb PLUS there is supposed to be an o-ring that sits on top of the clip to seal everything up.
CLARIFICATION EDIT: Yes, there IS an accel pump check valve arrangement in EACH carb...but the actual accel pump itself is only on the #2 carb. There are little hoses linking the accel circuit through each of the other 3 carbs.

BTW, the petcock seems to be a vacuum type(on,res,pri). I now have to figure out why and what else has been plugged. Could this cause or be part of my original problem ?

The petcock could have had problems with a failed/holed automatic shutoff diaphragm which wouldn't open up to allow fuel to flow AND which may have allowed air into the #2 cylinder through the vacuum line. Hence the plugged off vacuum line. Then the PO just ran the bike with the lever turned to PRI. This petcock lever position allows the fuel to flow WITHOUT any vacuum needed.

Thanks for the response, H2RICK. I just went to town and bought another T to go in line to put everything back and try it. Is the petcock suppose to run on PRI ? I did not notice what the petcock valve was turned to. I figure if it does not act right I can always plug the line back. Strange that #4 vacuum was still hooked up. I really don't understand this vacuum system anyway. I've just cleaned the tank and I'll try cleaning the petcock before installing the tank.

One other thing, those bearing and brass rods were in all the carbs (except were one was missing the clip and ball). I don't know what kind of problem that one missing will cause. Do You ?

Is the petcock suppose to run on PRI ?

Nope, the PRI (PRIme) position is there to bypass the normal vacuum operated shutoff ONLY if the carbs have been worked on off the bike and/or if they've been drained for whatever reason (winter storage, etc.). You would then need to PRIme the carbs with fuel to get her running again.
You would normally run with the lever in the ON position or REServe position depending on how much fuel you have in the tank.

I'm not sure why you'd need another tee unless you have TWO fuel inlets to the carb rack. Typical 650's only have ONE inlet in the centre of the rack. Most 650's have the vacuum port/hose for the petcock on the #2 carb. I am not aware of any 650's using #4 for any vacuum takeoff at all. There should be 2 vent lines....one between #1 and #2 and then another one between #3 and #4. These are strictly for equalizing pressure in the float bowls so you don't get any kind of a vacuum lock in there.

One other thing, those bearing and brass rods were in all the carbs (except were one was missing the clip and ball). I don't know what kind of problem that one missing will cause. Do You ?

My WAG, but without the ball, you will not have a proper non-return action for the fuel coming from the accel pump....so all of the fuel may NOT get to where it's needed in that particular carb.....making your acceleration on that cylinder somewhat sluggish compared to the other 3 carbs. Kawasaki and Mikuni put that check ball there for a good reason, so I'd be putting one back there (and its clip) to make sure you get proper balanced acceleration.
My .02 worth....

Thanks H2RICK, I plugged BOTH 1&4 vac hoses (were I replaced then removed the Tee), removed all larger hoses and plugged air box. I assume I can run petcock on PRI while capping vac outlet.
I guess I'll have to pull the carbs back off to replace ball and clip. I just stuck the brass pin in the hole and put the bowl back on. Another dumb guess ! The PO must have lost the parts when he worked on it. I found the brass pin in the bowl when I took it off. Reckon were I'd find another ball and clip ?

I think that #4 vacuum port MIGHT have been used to run the air diverter valve for the clean air system. Do you still have the reed valve covers with the spigots on them on the front (exhaust) side of your valve cover ?? If the covers are still there but the black coloured air-diverter valve is gone then some PO has made some "horsepower" mods without really thinking about the whole thing.

Reckon were I'd find another ball and clip ?

For exotic little bits like that, you might want to post in the parts wanted section. I'm sure there are members who have racks of 650 accel pump-type carbs laying around that they would rob for parts for you.
Failing that, you'd have to try your local Kwakker dealer for the parts you need, which are:

The clip is actually called "clamp, spring, check valve" and is part #92037-1123.
The ball is called "ball, steel, check valve" and is part #92140-1003.
The oring is part #16038-016.

I have NO idea if these parts are still available through Kawasaki or not but you won't know until you check.
A word of advice: If you deal with a big-box type of dealer, do NOT tell them that these parts are for a 30 year old bike. Most of them will just punk you off when they find that out. Just give the the part numbers and quantities you need and see what they come up with. Good luck with your search.

Thanks, H2RICK ! It's app.40 miles to Mobile,AL, nearest Kaw dealer. I'll search parts wanted first.

One problem, can't find category for 'parts wanted'.

One problem, can't find category for 'parts wanted'.

Sorry.....Run an ad in the "Classified" section which you'll find at the top of your main page. I'd title it "Wanted: 650 carb parts" or something like that so folks know you actually want to buy stuff.....rather than sell stuff.
See what floats back.....Good luck.
BTW, if you measure that check ball, you MAY find it's a common size. A lot of bicycle repair shops have loose balls in various sizes so you may find something that way.