Pod filters re jet cv carbs

OK! Since no one likes 400's on here, or cv carbs, i decided to make a thread for re-jetting cv carbs for pod filters..... I have a 78 kz400 b1

Today i got my bike started for the first time with dual carbs(was running single carb conversion). i re-jetted the main to 100. It was originally 95. Kept the pilot just stock, which was 35 i believe(wasn't labeled). So i got it running and sounding quite fair. When i drove around and got up to about 3.5k rpm it went flat and wouldn't accelerate anymore. When i pulled the new plugs out that i put in, they were pretty black, so it looks like i have a rich mixture. but this doesn't make sense. The stock jets were 95(which i believe is the next step down from 100). but they were meant for a stock airbox. Maybe it has something to do with the diaphragms... idk...
ANY HELP WOULD BE GREATLY APPRECIATED.
thanks

Then try one step smaller than stock.
Also make sure the filters do not block the bleed holes in the ventri.

im not sure what that means?

On some/most CV carbs, there will be atmospheric pressure vented to the bottom side of the CV diaphragm (or piston on older KZ400's). Some pod filters have a reduced diameter on the throat which will cover the opening. The opening is at the mouth of the air horn. Make sure the filter leaves clearance so the vent is unobstructed. It may be a large oval shaped port right at the top of the air horn.

If it gets blocked, the slide will rise very slowly or not at all. However, the problem of a slide not rising is far more commonly due to a puncture in the diaphragm. A new Kawasaki one will usually cost over $100 each (good reason to not like the diaphragm Keihins). There are several sources for getting just the replacement diaphragms, but it takes some tinkering and doctoring to do it. The diaphragms were not meant to be changed. The kz 400 forum has a sticky post on it, I think.

There is a chance that the slide is not the problem, but you should check it. Take the filters off and have someone work the throttle while you get all the way behind the bike with a flashlight and look into the air horns while someone revs it. The slides should go up and down together. By half throttle or sooner, they should be max open. If they are uneven or not fully open by half throttle (there will be some lag time), check the diaphragms. I say get behind the bike, way behind, because if there is a backfire, flames can shoot past the back end of the bike (seen it many times). You do not want your face up close.

Like I said in the other thread, I've only done pod tuning on the piston Keihins, so the diaphragm ones may differ, but I did have to alter the air jets at the top of the carbs for them to work right. I don't know if the diaphragm carbs have change-able air jets though.

By the way, there are more than just two jets to mess with. I think your jeting is as follows, or similar:
1977 CV32 (I think 78 are similar if not same)
Primary main jet: 70
Secondary main jet: 95
Slow jet: 35
Each jet has an associated air jet (non-adjustable, though, I think on your carbs)
Pilot screw originally 1-1/2 turns out (+/- 3/

Also, very important is the rubber plug for the slow jet. Make sure it is there and seals perfectly. If not, then there will be way too much gas into the primary main circuit.

Also, setting the fuel level and confirming the needle valve seals should be done before any jetting. If the fuel level is off, then changing jetting is a waste of time.

OK! this is very helpful. From what i have read, you are only supposed to increase the secondary main jet, and the pilot jet every three sizes of the secondary main jet. That's from what i found. That's why i didnt mess with the rest. Also, when i looked at the diagram of my supposed carbs, the diagram looked a little different. I did notice there is supposed to be a rubber plug, but i don't have them. also in the diagram it looks like the float valve is the same as the secondary main jet valve, but thats not the case. Finally, how do i set the fuel levels on these carbs??? thanks!!

The best way is to use the clear tube method which lets you see the actual fuel level. I beleive Patton (moderator on this site) has a good illustration of the method. A fitting gets connected to the drain screw port on the bowl and a clear tube is fitted and held vertically. Gasoline will be seen in the tube at the same level that it is in the bowl. The tube must have at least a 1/4" or bigger diameter at the point where the gas level is otherwise capillary action will give a false reading. Since the tube connected to the carb may be rather small, I just stuff the small tube into a bigger diameter tube so the reading is accurate.

Someone on the 400 forum may have a source for the rubber plug and/or confirm that you need one.

On the earlier carbs there is a metal clip inside the bowl that holds in the main jet and presses on the rubber plug so it doesn't fall out. You carb may or may not have that clip. Check with the parts diagram in case you should have that too.

It may be best if Patton can move this thread to the carburettor section so more carb-people may see it, rather than in the engine section.

That would be great. Yeah i dont think mine has a metal clip because i cant even get the nozzle to the primary main jet out....i unscrewed the primary main jet, and tried to pull out the nozzle...but it wouldnt budge.
That would be great if we could get it moved. I don't know why i posted it in the engine section....
here's what im talking about...
all the way to the left you have main primary jet and nozzle. middle you have the rubber plug. and to the right you have what i was talking about where it shows the secondary main jet and the float valve as the same thing?????

WELP NM ILL POST LATER

also how to i higher or lower the fuel levels...im guessing that's how i just check them correct?

loudhvx you are a genius. i put the rubber plugs in the pilot jet hole, charged my battery, and rejetted to secondary main jet 90 and pilot 35(stock). used the electric start, and it started and idled like it was right out of the showroom. YOU RULE. so i have come to the conclusion that my jets were too big causing a rich mixture and eventually flooding. Im not sure what the rubber plugs that go in the pilot jet do, BUT THEY ARE REQUIRED.

so for anyone wanting my current specs for my 78 kz400 b1 cv carbs they are
secondary main jet #90
pilot jet #35 (with rubber plugs!)

i took out the spark plugs and did not notice any white, but it was getting dark out. will update tomorrow.

i also found out the stock jets for these carbs are #85 2nd main and #35 pilot(slow) jet
those are really the only two you should change.

Thanks for update. That will be some valuable info for folks running the diaphragm CV's on KZ400 twins.

Would appreciate further updates when it is fully dialed in.