Mikuni 29mm Jet Size

Can someone tell me what the pilot jet size should be on a stock KZ900 with pods and V&H pipe with no baffle ? Mine are showing @25.

What are you referring to 'showing at 25'?


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That is what is stamped on the pilot jet.

I was under the impression that a stock KZ900 running Mikuni 29mm carbs with pods and a V&H header with no baffle would need a 120 main jet and either 17.5 or 20 for the pilot jet. Correct me if I am wrong.

If the pilot jet is too large, wouldn't that lead to the plugs being fuel fouled ?

Sudco recommends 25s (but they also show that for KZ650 through 1000s so I don't know) but a lot of searching (over the years) has shown folks on here are running 17.5s and 20s like you say....... I can't get anything to come up on search so I don't know if the update lost em for now or what. The removal of the baffle changes things too and unless your at the strip it might run better on the street with it in.

Goggle smooth bores and KZR and you should get some things to read. Too high of a setting for the fuel level, leaky float valves and or dirty low speed air passages and air screw settings could be part of the problem too but it could be the pilots just as well.

This used to be on the Z1E site:

gd4now wrote: It is my understanding that there were at least 3 versions of the vm29s offered. the A2, A7 and A12. There should be an ID stamped on the flange either below the choke lever, or on the other side of the carbs something like the following
29
A2 - this second line could be any of the other types noted above

IIRC the throttle valves have a larger cutaway on the A12 than the other 2 do. The A2 has a smaller pilot jet (17.5) than the others and a smaller needle jet than the others.

When in doubt, would start with 17.5, and test for best steady-stable idle, strong pull-away, and good performance throughout the 1st quarter throttle range. When properly tuned, the smoothies should be almost as user friendly as 26mm manual slide Mikunis (at least when using the stock airbox).

Good Fortune!

I received the #17.5 and #20 pilot jets. While waiting for the jets, I checked the valve clearance and they were all good. I also checked the float levels and adjusted them as needed. After receiving the jets, I installed the #17.5 jets. Started the bike and after letting it idle for a few minutes, then checked the plugs. The #4 plug was dry and sooty. I have dried with the air screw turned 1/4 turn out and up to 1 1/2 turns out, but still showing the #4 plug sooty. The other 3 plugs show no soot at all. Could the pilot jets be too large ? Do I need to go to smaller pilot jets ?

BIGKEVIN wrote: I received the #17.5 and #20 pilot jets. While waiting for the jets, I checked the valve clearance and they were all good. I also checked the float levels and adjusted them as needed. After receiving the jets, I installed the #17.5 jets. Started the bike and after letting it idle for a few minutes, then checked the plugs. The #4 plug was dry and sooty. I have dried with the air screw turned 1/4 turn out and up to 1 1/2 turns out, but still showing the #4 plug sooty. The other 3 plugs show no soot at all. Could the pilot jets be too large ? Do I need to go to smaller pilot jets ?

Do I need to go to smaller pilot jets ? --- NO, at least not yet, imo.
Would look for other reason(s) why #4 combustion is insufficient.

Were carbs bench synced?

Tried a brand new spark plug in #4?

Does idle rpm change when #4 pilot air screw is turned?

Good Fortune!

I took the bike out for a little ride today. The bike ran good from about 3000 rpm up. From idle to about 3000 rpm, the bike felt sluggish. After getting back, I checked the plugs and they appear to be clearing up. I didn't take the bike for a long ride today, but hopefully Saturday I will be able to get out for a little longer ride. Any ideas on why the bike would be sluggish up to 3000 rpm ? The carbs have been bench synced, but not the running sync yet. The rpm does change when the air screw is adjusted also.

On my kz900 I got 120 mains and 25 pilots with a kerker 4-1 and Z1 air box.
I first use 17.5 and the 20 and back fire from 3500 to 6k then it would clear up.
Air screw at 1/4 turn out...any more then that if I blip the throttle it boggs
1200-1500 rpm idle

spdygon wrote: On my kz900 I got 120 mains and 25 pilots with a kerker 4-1 and Z1 air box.
I first use 17.5 and the 20 and back fire from 3500 to 6k then it would clear up.
Air screw at 1/4 turn out...any more then that if I blip the throttle it boggs
1200-1500 rpm idle

Do you have 1.5 or 2.0 cut away slides?