29mm carbs running with air srcew closed

I have a very healthy stock 78kz1000 with a kerker header running mikuni 29mm smoothbores

the carbs have open velocity stacks
I run 115 mains
17.5 pilots
needles are at their leanest clip position
air screw is happiest 1/4 -1/3 turn
plugs are spotless
the bike idles great,mid range great ,top end pulls red line strong
these settings are very sensitive 1 clip richer and plugs start to load up
22 pilots and engine doesnt rev crisp ,bigger or smaller mains upsets the engine,air screw beyond 3/4 turn wont allow engine to
have crisp idle reving

these are pretty much the leanest positions except for the air screw
heres the kicker ..... runs flawless in cold weather(leaner) and I can run full choke at hyw speeds
with( air screw completely closed )bike will idle with very lite throttle bleeping
all signs say more fuel but if its done through needles,mains or pilots it runs bad

not to be rude but (solid theories only)
dont cut and paste from Z1 enterprises or sudco I have seen all the settings
also have no need for settings from other members bikes
would appreciate solid input from qualified tuners or anyone that had same issue

?

I do believe that the more pilot or the higher the pilot number the less air screw turn you need.

When I tuned my RS34 carbs, this was the case. At 15 pilot I needed 3/4 to 1 turn on the air screws to get 11.5 AFR.

Moving to 20 on pilot improved idle and reduced air screw to just a 1/4 turn to get 11.5 AFR.

I run my engine idle fat or rich at 11.5 to 11.8 AFR to help keep the air cooled engine cooler. So with the AFR cycling numbers, I can see just where the mixture is by digital number readout.

With pilots at 17.5 this is not right. You should be good at 17.5 and wonder if pilots could have been drilled out or miss-marked. I was confused that the more pilot the more you had to increase the air screws. Maybe our carbs work different. Cope tuning tips have you at 17.5 pilot with your setup.

Question, can you go to big on pilot and run on almost no air screw turn ????????????? as you see in my case, I went from 1 turn down to a 1/4 turn? If I went to a 22 pilot, wouldn't air screw be almost closed.....maybe 1/8 turn?

Are the air screw seats damaged? I'd color them with black marker, put the all the way down and see if they seat all the way.
Steve

Sounds like he's stepping over the pilot circuit.
Steve

Get a professional to clean your carbs...
Ain't got notion to do with the niddle clip , pilot , main nor stacks.
Iv run two bike with 29mm ...clip on 3rd slot ..120 mains 17.5 pilots .9 air jets stacks and 1 3/4 turns out on air screw.

From his last paragraph. :huh:
Steve

Valve clearances to specs?
Results of clear tube test?
BS30/97 air jet may require cleaning and/or replacement.
Perhaps enrichener circuits aren't perfectly clean..





Good Fortune!

The air screws on the vm29s have a small hole near the tapered end that the other Mikuni carbs air screws do not have. Due to this hole they work somewhat differently than those without the hole do.

Just keep in mind that on a Mikuni VM series carb an air screw controls how much or how little air is allowed to mix with the fuel pulled/pushed up into the pilot jet. So it has a direct effect on the air to fuel ratio in the pilot circuit.

My 33's have this too. The PO soldered them closed. I've yet to reopen them. They also appear to have been sanded. My air screws work to a point but are useless after that. I can only hope to find similar ones due to the 33's being discontinued.
Steve

Patton wrote: Valve clearances to specs?
Results of clear tube test?
BS30/97 air jet may require cleaning and/or replacement.
Perhaps enrichener circuits aren't perfectly clean..

Good Fortune!

Patton, do you happen to have a diagram of the Mikuni 33mm smooth bore carbs? I'm interested in seeing how the hole in the screw tip aligns with the passages.
Steve