Jetting carbs

Ok Looking for the right jets...

1981 KZ750 4 LTD

Carburetors; (4) Keihin CV34

Four K&N style air pods.

I also have the stock pipes on, but I have taken half of the baffels out of each pipe.

So my question is what type of jets whould i need to install?

This is what the bike is doing now; Starts fine and runs fine and runs fine on freeway.
The problem is on take off I need to feather the gas and let the clutch off slowly like a drag bike or the bike will stall out.


Thank you guys!

Post edited by: Johnny Red, at: 2008/01/09 02:04

Post edited by: Johnny Red, at: 2008/01/09 02:11

Works for me with K&N and 4->1
Carbs are Keihin CV34
Make sure pilots and transition holes are perfectly clear




Post edited by: JR, at: 2008/01/09 08:18

You have three jets in your CV34... #35 slow jet which has no replacement available, #62 main jet and the secondary main jet (which is the one JR marked with #135 in center). I recommend a #68 or #70 main jet and #140 secondary main. The main jets are hard to find but seem to be out there. Try z1enterprises.com for the secondary main jets. You may have to call to get them but they have them I think. You will have to drill out the plugs over your mixture screws in order to adjust them properly. The pilot circuit on your bike is too lean since you have modified the intake and exhaust and adjust the mixture screws will help. Also, using the larger main jets will help. Your mix screws will be about 1.5 (+/- .5 turn) turns out from lightly seated when adjusted correctly.

Thanks you guys!, I will print this out and start working on it.

To comfirm I will get #62 and #135 or are those the stock #'s.

or will I need to go to Main Jet #68-70? and Seconday Main Jet #140?

PS, Im at SEA LEVEL, Carlsbad, CA 92008


Johnny Red

Post edited by: Johnny Red, at: 2008/01/09 17:37

Post edited by: Johnny Red, at: 2008/01/09 20:45

#62 might be stock - cant remember. #135 is oversize. stock for that one is I think 125.


All I can tell you is that that's what works for me. On the other hand wiredgeorge is the carb professional and site guru and he recommends 68 or 70 and 140. It's up to you. You could always try both suggestions and see what works best. Jets are cheap. Z1enterprises definitely have the larger jets. not sure if they have the smaller.

Yes, I forgot about the mixture screws. Mine are at two turns out from lightly seated.

good luck

Thanks, I needed that info. I will order some jets now and get things going:)

The #62 main jets are the stockers for many versions of the CV34... If you add pods/pipes, the bike will start and run with the stock pilot jets (when you adjust the mixture screws) OK but starts and runs through mid-range much smoother and with more power with the larger main jets I suggested. It won't hurt to use the #62 mains but the #68 or #70 are better, in my view (after a bunch or testing). Problem is finding these jets. The secondary mains have us a few points apart but I test to redline and the #140s pull cleanly to redline without being too rich. Without looking it up, as JR noted, the stockers are smaller.. You will NOT be able to pull redline cleanly with the stock secondary main jets and pods/pipes.

can a mchine shop fab these #68 or #70 mains up and will they be the same?

Oh well, wifey didnt stock up the bank acct full of my play money, i unfortunately have to stock it up myself tomorrow and buy all this stuff then.

Have to dig out my carb supplies and have fun tearing into the bike again, gonna be like old times. :woohoo:

Randy, I got your notes over on my forum and will answer in a bit... thinking.

Well, i just ordered my Jets. If these dont do it i am sending them to ya George.

I ordered the 135 & 140 secondary jets and some #70 & 65 or something Mains.
One set of each size so i can have options.

Will install the 70 & 140's first though and tuck the others away in my Safe lol!:silly:

So its true, if you take the time and call Jeff in person. say who you are and your username here at Kzrider he will actually talk to you and he is a gentleman on the phone also.

Just make sure you hit the #2 option for technical assistance when you call. Then ask for Jeff. Phone numbers on his website.

patiently awaiting my package now........Jeff is it shipped yet? LOL!

Post edited by: ran429, at: 2008/01/22 18:00

While the 62 and 135 have worked fine for me in the past I decided to order some 68 and 140 and see for myself how they work out. I'm open minded on this and besides at $2 each jets are cheap. I'll be watching for any better performance and also hoping they wont be to rich and soot up. With the jetting I have my plugs tended to be a smidgen on the sooty side until I did the coil maod a couple of years past.

I figure by about the second half of March the snow should be gone and the temperature high enough above freezing so I can get the bike fired up for another season.
Hoping we can compare notes in a couple of months time