How do you use the choke?
I've always found full choke and NO THROTTLE will start it immediately every time from cold, then back off the choke as much as you can as soon as possible while maintaining a decent fast idle, say between 1500-2000. Ride off gently as soon as you can, don't leave it warming-up.
With a lot of carb bikes, I've found if you touch the throttle at all with the choke applied, it won't start.
When the engine is warm, no choke and just a touch of throttle.
I only do without the choke from cold if the weather is really warm, if it'll start from cold easily without choke then it's probably too rich
