[embee]

Cold starts (properly cold) should need choke, if it'll start without choke it's running richer than it should be. The choke is there purely for cold starting, it's not an ornament.

The main thing with the curvy is to make absolutely sure the choke cables and plungers are working properly. The only way you can be really sure of this is to take the plungers out of the carbs and check the cleanliness, that the springs are not broken, and the cables are free and well lubed.
The rear carb is easily accessible, the front one isn't and the only successful way to get to it is to take the carbs off, not a big job.

When starting from cold, apply full choke and DO NOT TOUCH THE THROTTLE. This is important. If you use the throttle when using full choke it will mess up the fuelling and then becomes a pig to start.

Full choke, no throttle, short prod on the starter usually gets it firing but as often as not it will stall after a second or 2. This is because the fuel in the float bowls tends to evaporate when parked up hot. The idle circuit and choke will have enough fuel to run it for a second or 2, but the fuel pump takes a touch longer to refill the carbs fully. This is perfectly normal.

Once started leave the throttle alone, and ease off the choke gradually as much as you can while keeping the engine running smoothly. Don't leave it idling to warm up, just ride off as soon as you can reasonably gently and get the choke off fully as soon as possible. Make sure your hot idle is adjusted to around 1300rpm, some people prefer it slightly higher, 1400 say.