Need help Mikuni VM29's on 78 KZ1000 with 1075 kit

I hope someone can help me, I have a 1978 KZ1000 that has a 1075 kit in it and a set of Mikuni VM29's on it. The jets are: 20 pilot jets and 120 main jets. The needles are in the third notch or the middle. I've had the carbs ultrasonically cleaned.

The problem I'm having is that when the bike is cold it spits and misfires for about 2 to 3 miles then seems to calm down and runs fairly smooth, but if I come to a stop sign I have to bump the throttle to get the idle to drop from about 2200rpm to 1500rpm.

I need to know if I should replace all the soft parts and the needles, jets, floats, ect., or if I might just need more adjusting?

Thanks for the help,

Dirk

TexasKZ900 wrote:

...1978 KZ1000...1075 kit...Mikuni VM29's...20 pilot jets and 120 main jets. The needles are in the third notch or the middle. I've had the carbs ultrasonically cleaned.

The problem I'm having is that when the bike is cold it spits and misfires for about 2 to 3 miles then seems to calm down and runs fairly smooth, but if I come to a stop sign I have to bump the throttle to get the idle to drop from about 2200rpm to 1500rpm.

I need to know if I should replace all the soft parts and the needles, jets, floats, ect., or if I might just need more adjusting?....

Probably just more adjusting.
Might have air leak, perhaps through old carb holders, loose clamp, etc.

Or possibly throttle cable hanging for whatever reason (could assure some slack allowing full slide closure).

Would also assure automatic advancer is functioning correctly. Clean and lubed and in otherwise good condition. Not sticking or hanging due to rust goo or whatever.

Possibly pilot air screws need adjustment. Could experiment by enrichening (turn screws in, say 1/2 turn and test run.) If worse, lean pilot circuit by turning screws out (adds more air) and test run.

Were carbs bench-synced? And again synced after installation with engine running?

Good Fortune!

Thanks for the info, I’ll try adjusting and the air screws and going for a test ride. The carbs were not bench synced, but I borrowed some Morgan tubes (I think that’s what their called) from a friend and synced them.

Do the air jets in the front of the carbs need to be adjusted, or do they just go all the way in?

What type of lube should I put on the advancer?

Thanks,

Dirk

TexasKZ900 wrote:

...Do the air jets in the front of the carbs need to be adjusted, or do they just go all the way in?
What type of lube should I put on the advancer?....

Most any lube is okay on the advancer, but I prefer moli-grease which seems to last a long time.

Air jets just screw in.



Good Fortune!

Thanks,

I'll let you know what happens.

Dirk

are your air mixture screws set 1/4 turn out from just easy seated(turned to stops)

could be a tiny piece of grit somehwere in your idle circuits...even though cleaned..stuff has been missed or pushed into a knook and dislodged when gassed up ,by other folks (like me) and upon a second cleaning of the idle circuits they are better....

i have heard of some makes of pods obstructing a flow hole that is visible with the pod off(on the outer back rim of the air intake side)

popping can be a clogged or partially clogged idle circuit...

all of these things have happened to me on my 29 mikuni smoothbores(except the filter rubber touching the air passages)and at the time i was sure they were cleaned great....it was kinda depressing to not have it sorted,but a second cleaning was all smiles...they are pretty much set and run ,problem free carbs,i think your jetting while not maybe pro perfect(or maybe)is not the root of the stumble to return to idle and the popping on deceleration.....i think somethings in the idle circuits imo

good luck...cool pipe mix and match..i have a morwaki titainium mid pipe and aluminum hand made racing canister combo (pictured below)that i am gonna have fabbed onto a kerker header...inspiring to see your job on yours...and nice clean motor finishes...craig

Thanks for the info, I've tried to set the air mixture screws at a 1/4 turn but it pops and sputters even more as I apply gas becoming less noticeable the higher the gear. So I have the air mixture screws set at one full turn out right now.

Something is plugged up in the pilot or idle circuit. My 1105 is the same except for 17.5 pilots, mixture screws 1/4 turn out & it runs perfect

Thanks, I'll pull them off the bike this weekend and make sure their clean.

Dirk