Hi, I battle to kick start my bike. It starts easily using a drilling machine on the rotor. What I've done.

1. New carb. Cleaned it after installing the new Clarke tank.
2. Rebore with new piston and rings. Compression 75psi.
3. Ignition is HPI. The timing is correct. Good spark.
4. Once running it idles well.

I don't know what else to do other than clean the jets again. The carb was overflowing, now that's fixed. Some debris in the seat.

Any suggestions?

Does this carb use a starting circuit and not a choke? If so, did you confirm the passages are clear after your carb was cleaned? Is it only difficult to start when cold? If so, try putting it in 2nd gear, engage the starting lever, rock it back and forth 10 times to pull in mixture then put it in neutral  and give it a good kick. My larger 2 strokes responded well, but you usually don't need to do this on a smaller bike.

I find it remarkable that you are able to spin it at all with the spark plug installed, and even start it, with a drill motor. 

Did you verify the jet sizing on the new carb? They are probably the wrong size if it's a cheap Chinese replacement. I remember my IT200 having a choke and starting cold in 3-5 relatively easy kicks.

It's a Mikuni carb. Original. I'll check the jet sizes.

The drill struggles to get it going. Not cordless drill. Once it gets over the compression stroke it spins.

Make sure when kicking you aren't twisting the throttle open. Opening the throttle makes the starting circuit ineffective. (You probably aren't touching the throttle when using the drill)

The jet sizes are as follows:

main jet 260.
Pilot jet 35.

According to the manual main jet #330. Pilot jet #55.

It starts so easily with the drill. Choke and no throttle.

It's easy to have a habit of twisting throttle while kicking without even realizing it which is why I mentioned it.

The two jets you mentioned are significantly different in your "new" carb, which doesn't make a lot of sense unless it's not actually new or not specifically for your bike?  In any case, there are more calibrated parts in the carb that work together as a system... venturi size,  needle and needle jet, and slide cutaway differences can make a difference in main and pilot jet requirements.  In other words, good idea to check all the calibrated parts, not just a couple of them.

Correct me if I'm wrong, but shouldn't that engine make at least 110 to 125 psi of compression? If so, I'd test with another compression tester. I've had certain compression testers read low like that on small engines. Other engines I've worked on were truly low, and would refuse to start unless I spun it up with a drill, or push started it. Does sound like compression is low to me.