Need some advice about re- etting my VM 29 pumpers

Bike Z1B 1015CC, stock airbox with K&N filter, bike runs great with the VM 29 pumpers but the plugs remains a little sooty, carbs are synct, all clean, float height checked, plunjers new etc.
Main jets are #120, air jet .9, pilot jet 20, jet needle 5DL31-3, needle jet 0.6, throttle valve 1.5, starter plunjers are new.
I played a little with the airscrews from a 1/2 to 1 1/2 out but not enough succes.
Now am i thinking of jet changing but where to start first?
Pilot jet to 17.5  or main jet to #115 or air jet to #1.0 or disconnect the the accelerator pump (although works great when accelerating)
What is the best order to start with?
 
 

At what rpm's is it sooty ?
If you haven't done plug chops then the plugs will only show running conditions at idle which indicates possibly a smaller pilot is needed.

What heat range plugs are you running. If your plugs are to high a temp range they may not be getting hot enough to self clean.
A bit counter intuitive but a higher range heat plug needs a hotter running engine/lean mixture to be able to self clean. 

Is VM29 pumpers a typo?  Did you mean VM28 pumpers?  

Assuming so, the VM28s came stock with much smaller jetting than you installed.  15 pilots and 105 main jets.  Running a stock airbox and 20 pilots and 120 mains is a huge step up in extra fuel.

@ ZED1015, no i did not a real plug chop, i ran the bike for about a 120km between 100 and 120 km/h and then cheked the plugs. Last month i cheked the plugs several time and i noticed they stay a little sooty, changing the pilot airscrew a little (1/4 to 1 turn out is the best) helps but not enough. Your suggestion for a smaller pilot jet was also my first idea.

@ Warren3200gt,  I use the NGK-B8ES plugs,  maybe thats a start to go to NGK-B7ES

@Nessim, No not VM28 pumpers, they are Mikuni VM29 smoothbores with an accelerator pump.

I think i am gonna pull the carbs off this weekend for inspection and start with the pilot jets.
Thanks for sharing the ideas.
(to be continued)

willemZ900 wrote:

@Nessim, No not VM28 pumpers, they are Mikuni VM29 smoothbores with an accelerator pump.

 

Wow!  I've never heard of those carbs before.  After reading your response above, I did a google search and turned up a page that mentioned that the pump parts were an add-on kit.
 
You have a very rare set of carbs there.

www.redlinecycle.com/Carbs%20-%20VM29.html

Like you Ed I too have never seen vm29ss carbs with accel pump.  I would guess it was an aftermarket system but do not know this for a fact. Would love to see what it looks like. I do have a pic of some vm28sc carbs with a pump here it is.



The other thing I will say is the air screws on 29s don't behave the same way as on other VM series carbs because of the hole in the screw towards the tip.  1/8 turn out is about right for #17 pilot jets. 

Guys if you want to see pictures, Willems bike was the April BOTM 

When ordering a set of smoothbores you could specify their spec and jetting.
The accelerator pump was one of the options from the factory but not too many sets about relatively speaking.
 
  

Thanks for the pic and the fact you could order them that way.  I had no idea that was so.

FYI
Yesterday evening i start reading a old 1979 Mikuni tuning guide (Mikuni carburetors, parts & superbike performance products from Jam trading inc) witch i had for year on the shelve and never read (SHAME ON ME).  And i found someting interesting i did not know, there are three types of VM 29 carbs.
VM29-A2: main jet 115, pilot jet 17.5 ,  for sligtly modified engines. Kawasaki 900 Honda CB750 thru '78
VM29-A7: main jet 120, pilot jet 20 or 25 , for big bore and/or super modified kits
VM290A12: mainjet 115, pilot 25 for Suzuki GS750,1000
All three models use the same power pump model ACP-4
Main difference between the models is the Throttle Valve Cutaway (1.5, 2.0, 2.5)
So today beautiful weather, i could not wait and pulled the carbs. I decided to switch the mains instead of the pilots ( rev to VM29-A2) Changed the main jet from 120 to 115, turn the airscrews 1/4 out. And made a test drive for about 25km. Difference??
The bike was already fast but now it pulls a little better, throttle response is also a little better, stationair at 1000 rpm the engine runs pretty regulair. Checked the (new) plugs and they all look nice, no soot anymore. I am satisfied now.
For the near future driving i am gonna play a little with the airscrews to look for optimal response/result 

Accelerator pump kit was a accessory for both 29's and 33's.



Never ever heard of VM27 Smooth Bores, must be very rare! Not sure what year this add is from.