Carbs coughing at low speed

Hi can anyone help with a problem I have with my 1976 z1 900. Got the usual stuff done to it Wiseco 1015 cams big valves mikuni 29mm smoothbores what’s happening is it starts first go it ticks over fine the plugs are a good colour it’s when riding if you’re moving at a steady speed 40 50 60 it runs a bit rough and you get spiting from the carbs but as soon as you open it up it flys should I be looking at the Carbs all the timing 

Stunning Harris (Magnum II ?) I may come calling for a BOTM feature 

Could be several causes but the usual suspects are a lean condition , valve clearances or  ignition timing.
The speed range it affects means very little though.
You need to identify the throttle position it occurs at to isolate the fuel circuit that is causing the issue if it is the carbs.

I am running vm29 too, what are the mains, pilots and how many turns of the airscrews?

Hi 120 mains
17.5 pilot 
0.9 air jet 
air screws are only just open about 1/4 to 1/2 turns out I’m using foam filters 
do you think I need bigger pilot jets or smaller air jets

Hi it’s a magnum 1 
it’s the 10th one made iv had since 1979

Hi thanks for your reply 
bike is only done 250 miles since rebuild so the valve clearances should be okay The problem is only When throttle is partly open so I’m guessing it’s the pilot circuit the air screws are only turned out between 1/4 and 3/4.carbs 2and 3 are open the most as the tank smothers them a bit . As for the timing am using dyna s and dyna coils with the timing on full advance thanks 

ps I’ve only just got back on the road after 23 years
 

This is me just after I got it 

malcolm9kevin@aol.com wrote:

Hi 120 mains
17.5 pilot 
0.9 air jet 
air screws are only just open about 1/4 to 1/2 turns out I’m using foam filters 
do you think I need bigger pilot jets or smaller air jets

Try a 0.6 main air jet..

That was my next try but could only get 0.5 so I’ve got a set of drills also can you get choke plungers ?

malcolm9kevin@aol.com wrote:

 also can you get choke plungers ?

Yes! I can repair your original plungers.
Either through my ebay listing or £10 cheaper direct via contact at - zed.1015@yahoo.co.uk

Mikuni Choke plunger VITON seal repair. KAWASAKI Z1,Z650,z900,Z1000,Z1R,Z1300 | eBay

malcolm9kevin@aol.com wrote:

Hi it’s a magnum 1 
it’s the 10th one made iv had since 1979

I love them, I had a Honda powered Magnum II a while back (20 years ago)