[Spokes]

1st thing to check is your "o" ring between the carb and the heat insulator. Replace it for good measure.

2.) Make sure you don't have a crack in the insulator.

3.) Make sure the gasket between the insulator and the head is good. Replace it for good measure.

Since you mentioned backfire, your timing may need to be advanced a bit.

If indeed you have 145lbs compression in both cylinders the engine should start in an instant.

Your description of hard starting sounds like a low compression issue.

My 65 CA95, built from scratch with 100% mixed parts has good compression after new bore/pistons/rings/wrist pin/valve seat cut & lap.

The bike starts in milliseconds in warm weather without the choke. In micro seconds with the choke when 35-45F Before the nice machine work, my bike started just like yours.... Just sayin.