I wish I could give a simple cure-all to obtain 1-kick starting. Unfortunately, I can not. I can tell you that when everything is right, they will start on a single kick most of the time. Here are some tips:
If the bike runs poorly, that must be addressed first. If it does not run well, it will not start well.
Buy, fabricate, or repair an Easy-Start system. It really helps to wake up the ECU with around 9 - 10 volts just prior to a starting attempt.
Use K-Scan to set the idle speed at 1400 rpm. This has a huge effect on starting and possibly overall running.
They like a vigorous kick. A lazy kick will never start the bike.
If you are not powerful enough to kick it with leg strength alone, you will need a flying leap and a straight-leg kick. This is the only way I can start my 280. I can often start my 250s with leg strength after they are warm – but I usually do not as it takes a toll on my knee.
The factory starting procedure says to use zero throttle. That is generally a good idea, but I find a bit of throttle at the end of the kick stroke will often encourage the engine to run.
Always select neutral. The clutch is too draggy to waste any energy trying to start the bike in gear.
Do not reposition the kickstart lever to “come up on compression” or something like that. I think that just confuses the ECU as it senses flywheel rotation. Just kick it from wherever it is in the stroke. This requires that you begin the kick with the lever at the top for a good full stroke. Do not reposition the lever to get a better angle on it.
If you are not very tall, give yourself a height advantage. Put your left foot on a log or rock. Alternatively, I stand on the left peg with the bike gently rolling downhill and kick.
A flywheel weight seems to aid starting, but it is not a huge difference.
If you can not get a good fast kick, you may have to consider decreasing the compression ratio. One of the first things I tried was using 2 base gaskets. But this has some disadvantages as it simultaneously alters the port timing and also increases the squish clearance. However, it is a way to see if machining the head for a lower compression ratio would be worth pursuing. Using 2 base gaskets also repositions the head slightly and I had to ream the muffler mounting holes to make everything fit. Officially, you must remove the engine from the chassis in order to remove the cylinder. I just elevated the cylinder and put a cut in the second base gasket to get it around the connecting rod. Some silicone sealer at the join made it leak-free.