OK,
Here goes....
First off: You really need to understand what circuit does what w/your carb.
Mikuni offers a tuning guide for this as all the circuits overlap some. (Do a web search and you will find it)
2nd: You jet/tune by throttle position NOT RPM
3rd: The big thumb screw adjusts your slide height which determines the minimum RPM the motor will run at.
4th: The "little" flat head screw is a pilot/idle air bleed circuit...when you turn it out, it LEANS the idle/pilot circuit.
5th: Where to start? Simple, make sure the bike starts.......cold w/the choke on and hot w/it off.
6th: Starting routine: Follow it......
Cold, leave ignition off/choke on and slowly run the kicker thru 4 times slowly to "prime" the motor w/the last time just at/close to TDC. Turn ignition on and kick thru like you are trying to break the kickstarter off......no sissy kicks.
Hot: Same routine except no choke and less "priming"
Now the million dollar question everyone has opinions on but I have never heard the correct answer yet....Why do Zillas need "the routine" and Banshees/250s/etc. don't?
Simple........ 2 main reasons.
First off whenever a carb sees airflow, fuel does NOT flow instantly as it takes a freckle of time to pull fuel out of the bowl, into the pilot circuit and be sucked into the motor....... The bigger the carb (like on a Zilla), the longer the delay, hence a "lean" spot on initial crank-up.
2nd and most important, whenever a 2-stroke motor is shut off, the vaporized fuel in the crankcase under the piston begins to come out of suspension. The longer it sits and colder the crankcase the greater the percentage. This results in a LEAN air/fuel ratio on the initial start-up as the air/fuel must go into the crankcase before getting pushed up the transfers into the cylinder which when lean WILL NOT start very well.
The BIGGER the crankcase volume (like on a Zilla 500CC motor), the harder it is to refill to the proper air/fuel ratio during a slow speed crank (kick)
This is one of the reasons we ALWAYS run a Zilla pilot/idle circuit on the rich side...
The other is when you chop the throttle at hi RPMs the amount of air,fuel and premix drops off yet the motor is still spun up and will start to seize unless it has enough lubrication.......
OK, now you have some basics.
1: Adjust/jet your idle pilot circuit so the bike starts hot and cold and the motor returns to idle immediately after you "snap" the throttle w/out revving more than a couple times before slowing down and will idle for about 30-45 seconds before it starts to "4-stroke".
If you have to adjust the air bleed screw to less than 1/2 turn out, your pilot jet is too small.
If you have to adjust the air bleed screw more than about 1 3/4 turns out your pilot jet is too big.
If AT ANY TIME the motor "races", IT'S LEAN........ pull the choke on immediately and hit the kill switch.
Ok, that's a start....
I'll post the rest later when I feel up to it.
$.02
RK