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Discussion Starter #1
Hi, I am repairing my son-in-laws 1978 KZ650B. From various pictures, it is a VM22 using #90 main jet and #50 pilot. Son is complaining of it bogging down mid-range. It looks like the previous repair guy didn't change the jets from the standard jets. My reference books/searches show #90 and #50s.

Any recommendations on what a pod bike had luck with? Thanks.
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Discussion Starter #3
I noticed the chart for a VM22 carb has a "pilot jet #15" and a "second pilot jet #50" listed. I see markings on the slow jet next to the main jet and it is a #50. Where the heck is the #15 pilot jet? I assume the second pilot jet is right next to the main jet. I appreciate the help.
 

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You will find some jetting info here along with other discussion on KZ650 and pods.

 

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Discussion Starter #5
Thank you for the reference on Pods. Apparently my US KZ650 is a B2A model that has these unusual VM22
MIKUNI KOGYO carb. My Cylmer service manual doesn't cover this carb. Searching on VM22 comes up with a variety of dirt bikes, not mine in particular. I can't go back to the regular air box, don't have it and it is owned by my son-in-law...leaving the pods.

Last night, I read a good article describing the idle circuit, the mid range and the high end. If my problem is midrange, it is saying to change the jet needle or raise/lower the needle clip. My idle seems to be good except on take off. It bogs down. Changing the clip after each ride to see the impact is a bit time consuming. Well, put there is 3 feet of snow outside in Chicago.

The knowledge also pulled, was if the plugs show a lean condition (white hot), the main jet should be bumped up a number. Sounds reasonable. I am surprised the previous reliable service guy didn't bump up the carb jet when he installed and ripped out the air box as his recommendation. So much for the reliable guy's mode, I guess.

The needle thickness is of interest to me should anyone have experience with these VM22 carbs.

Thank for the response. Regards John


Current spec / and in use.
Main jet 90
Pilot jet 15
Second pilot jet 50
Needle jet AO-7.4
Jet needle 5CL-10-4
 

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From my link:
as a general rule - 1 size on main jet - sometimes one size on pilot jet and occasionally raising the needle 1 notch.
 

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Discussion Starter #7
Just to clarify (I get confused)...to raise the needle 1 notch, I am placing the clip down 1 notch. I think by moving the clip down, it causes the needle to rest a bit higher. Correct? You are the second person to recommend I raise the needle.

I am opening up the carbs now and getting into the needle setting. The shaft retaining screw is stuck and I am soaking it to then pull out my impact screwdriver. I will find out soon what it current clip setting is.

More question, my carb kit has a needle but doesn't have the tube that the needles slides through. Only main jet attachment. I am tempted to not change the needle because it would mix a new needle with an old tube. No markings on the size of the needle. Any advice on whether to use the new needle or use the old one. Old one is not pitted.
 

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Yes. To raise the needle you lower the clip.
To make matters more complicated, Kawasaki has 4 different needles available with different tapers on them.
For now, I would suggest you stick with what you have and see if raising the needle helps.
Take plug readings to make sure you are not running too lean or too rich.
 

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Discussion Starter #9
Thank you for the suggestions. This is only the second bike carb to work on (amateur retiree) and the 1978 Kawasaki had so many more variations probably related to which country. Hard to pin down a good rebuild kit. I got what I got. It is missing the main jet tube as a replacement. Other kits didn't have it either. Same with the fuel needle not provided either. So far they look ok, not pitted or bad grooves. I will save the money on getting separate ones for now.

I didn't ride the bike enough to get a good read on the plugs. So far seems lean. I have popping backfires on the last run. I think that is air leakage and too lean. I have new intake boots on order and better pods.

Thank you for the suggestions.
 

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Discussion Starter #10
I pulled out the needle. Easier than my Honda CB350F where the retainer screw heads would not give up. These did fine.

Needle clip is in the center position 3. The needle and slide are burnt. See picture. Is this normal? All 4 are like this. I assume no one has been in here since 1978. Needle has a 5CL10 marking.
 

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Discussion Starter #13
Related question, how do you carb sync these? The adjustment screws on top are factory original set. The paint mark/glue is still there. I have air mix screws near the header, so they are actually fuel mix. They have a pointy end. Do you carb sync these guys with the air mix screw? When I removed the air mix screws, each carb had a different turn out count. 1 1/2 to 1 7/8 differences. The sliders on all 4 carbs look good about a wire width on each. It will be a while before I can get a carb sync vacuum setup going, but wondering how a guy would approach the problem. Thanks for the ideas. I don't think since 1978 anyone used the adjusters to sync them.
 

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Carb synch would be a long story and there should be lots of youtube or write-ups on the procedure already available so I won't get try to re-invent the wheel. You were smart to count the turns of your mix screws before removing them. Just set them back the way they were and see how it runs. You can always fine tune later.
 

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Discussion Starter #15
My prior experience with sync'ing was on a Honda CB350F four cylinder. It has adjustments just like this KZ650. I have 4 vacuum gauges with hoses to line them all up. I just tweak the adjustment to get the sliders up/down until they are equal. Now on this KZ650, the adjustments are sealed under factory glue/paint. No one has messed with this. The KZ650 is original owner's father, now my son-in-law. So we have history on it. Well, they treat it like farm equipment and just ride the bike. Not much dealer service out here.

Other videos, on a KZ650, the guy just leaves them alone. Is it the air mix screw that people use to tune the vacuum? Sync the carbs? I am guessing that is what you fellows do. Hook up the meters and adjust the air mix (fuel mix on this VM22 carb) to get them performing the same. Am I going the right direction? Putting in new parts and doing ultrasonic cleaning is certainly going to wack them to new turn out numbers. I appreciate the ideas.
 

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You have to break the paint bond in order to synch but don't assume it needs it unless you have separated the carbs.
I recently did a complete strip down of my carbs but I left them attached so the synch would not be affected. I put the carbs back onto my 1984 ZN1100 and it runs very well. I do plan to check the synch at some point but for now...I am following the " if it ain't broke, don't fix it" rule.
 

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Discussion Starter #17
I have not separated the carbs from the rack yet. Taking it slow. Thank you for the warning that separating makes a big difference on the adjustment settings

The observation is that in order to adjust using the lock nuts, you have to shut off the engine, pull the carb out, take off the cap, tweak it, try again. For the VM22 carb a little clumsy. Would be nice to adjust the screw while running and then lock it down. Taking the cap off brings in all that air and breaks the vacuum doesn't it? Is there a better way I don't see?

I can see manually sync'ing the carbs with a piece of wire to make the slides level. It gets you close.

On the plus side of separating the carbs, I can get at the fuel lines, change the rubber fuel tubes in-between and the O rings. Carbs are not leaking before I started. There are other rubber parts, I don't have either. A challenging problem.

I use the ultrasonic machine to clean after the tooth brush scrubbing technique. A little concerned not separating the carbs will just push the loose crud in places it can't get out. Taking it slow. Thanks
 

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Your last post made me do some digging. Your carbs are quite different and you may be able to separate them from the bank without losing the synch settings. But in any case, the manual says you adjust them while the engine is running. You do have to remove the fuel tank. Most mechanics hook up a small temporary fuel tank. With the tank out of the way, this allows enough access to the carb tops. You remove the tops and this allows adjustment without removing the carbs.

Don't forget to set up some large fans to cool the engine while you do this, and take care that the exhaust is vented outdoors of course.
 

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Discussion Starter #20
Thank you for the research. I still haven't separated them but spent time scrubbing the outside and getting the simple green & water heated up for the ultrasonic.

The picture above tells me the cap over the adjustments apparently do not impact the vacuum. So ok to remove then for the adjustment, if I have to. I do running the bike last week with a separate fuel tank / syringe tube and a quick release fuel line clip. I will have to add a fan because the engine does get too hot on the stand with no air flow.

So for procedure (if I need to), get carb together and warm it up some. Then pull remove the idle screw and pull off the caps, put idle screw back in. One screw is in the the way. I guess I can leave that screw off until done and save a step. Then hook up my vacuum pressure gauges. Restart and adjust away. That will work.

Thanks for the technique. I feel better about not changing the factory setting knowing that it can be as needed. I would have wasted my new boots with connectors.
 

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