Hardrider, I just went through this delema myself. The choke is not actually a choke like on a car. It is actually a fuel richener. There are three jets in each carb. The main jet, idle jet and the starter jet. The main and idle jet can be removed. The starter jet, which is key to the problem, is pressed in. It is the small brass jet by the main jet. This gets clogged very easily. You see, this jet fills a small chamber under the choke rod from the fuel bowl. When the rod is slid out of the way when you slide the choke lever back, the fuel in this chamber is pulled into the cylinder when it turns over. I had to use a very small stainless wire to clean it out. I used a wire cut from my wire wheel.

Disassemble each carb completely. Soak each carb in carb cleaner and wash off per instructions. Then poke the wire into the starter jet until it goes through. You will be able to blow air through it if it is unclogged. Once you do this it should fire right away and then idle. What you are doing by opening up your idle screw is allowing more air in to pull fuel in through the idle jet. Make sure you sync your carbs too. Smooth idle is also dependant on that.

I use two vacume gauges that I purchased from Harborfriegt for $12 each. I sync one and two, then three and four then two and three.

Hopefully this helps you. My bike runs like it just came off the show room floor.

Sounds like the carbs need cleaning...if its been stood for a while..petrol thats in the carbs goes off....so you will need to take the carbs of the bike & take the float bowls off to clean them out...& do the jets as well...has these have small holes in them .petrol goes threw these & gum up....thats why your bike wont rev!!..its not getting enuf petrol!!...hope this helps