Carburation.

[stephensmethurst]

The following facts may help those who experience "makes no difference" when adjusting the pilot mixture screw.
Inlet valve opens, piston descends creating depression. Say -15. Atmospheric pressure,say +15.
Slide closed means air is drawn through the bell mouth opening to the pilot jet and out of that small hole.
It does not matter one jot what position the mixture screw is set at. At all times during tick over the same volume of air
will pass through the system.
Here is the proof. Place a half inch copper tube in your mouth and blow air onto the palm of your hand.
Place a one inch tube in your mouth and do the same. The difference in pressure is obvious yet the volume of air
from your lungs is the same. Therefore, the mixture screw enlarges or restricts the pilot airway. The same amount
of air still passes in either circumstance but at a faster or lower speed. Faster speed draws more fuel.
The mixture screw should be called an air speed regulator if you ask me.
So "makes no difference" means something is wrong. Most owners know the usual culprits but there are rare causes
for this sympton. Mikuni bore airways and cap the bore hole with a pressed ball bearing. They fall out opening the circuit
to atmosphere. Other nuisances are the four lifter arms on the choke lever rail. Years of yanking them up and down bends
the lifter prongs. It only takes one cold start plunger to seat incorrectly and the cylinder has a permanent rich mixture.
You need advanced tooling to measure these problems which I made years ago ... Steve Snethurst

[rickm]

Thanks, this is all great info Steve.
I presume posted in response to my thread below?
viewtopic.php?f=4&t=46187

[stephensmethurst]

Hello Rick....My first post was aimed at folk trying their best to remedy difficult and vexing carb snags.
I am not expert at everything but you might try pointing an infra red beam at the four header pipes.
This will indicate which cylinders are hottest and coldest. Be warned, infra red does not like chrome reflective surfaces.

If the readings are within 20 degrees of each other that is acceptable and pilot mixtures are pretty good.
That type of carb and those fitted to Z1000's without an air mixture screw but with a fuel screw towards the
inlet spigot have a brass tube inside the pilot airway. It is a good idea and ensures a consistent volume of air.
I have measured many of them and can't get a different reading from one carb to the next.They always deliver
the same amount of air. The only adjustment you can make is to increase or decrease the amount of fuel entering
the inlet port.

A personal preference of mine is never fit NGK plugs. I use copper core champion. More expensive.
Long spark issues [when the spark jumps through the insulation to the side wall} are difficult to detect.
Years ago NGK were the best and probably still are when bought from an authorised dealer.

Sorry don't know what's wrong with yours, you have done all the basics and I wish I could help.