Starting Problems

I'm having problems with starting my scoot. It is a relatively standard GP200 setup, originally I had a 30mm delly and a casa megaphone exhaust, and it used to start & run very well. I did do a full rebuild last year, and it started & ran OK. I then had some starting problems, i.e., it may start first kick, but if not it may start on the 20th! basically due to flooding. I recently put a Scootopia 22mm carb on & it's no better, but I'm keeping the carb on. Last week at an open day I put it on a dyno, and apart from it being slightly rich on tickover(once I got it started), was good all through the rev range, and giving 12 HP at the crank. I've fannied around with the pilot & mixture screw to no avail. I then found that it would start with the air filter off, and once warmed through I could replace the filter and it runs sweet as a nut, but lean with it off. The question is could it be a weak spark, when kicking, stopping it from catching unless it has a lean mixture, but once running the flywheel is rotating faster giving a better spark. This possibly being caused by a de magnetised flywheel, or too low or high pickup. The BGM LT coil is 530 Ohm & the pickup is 112 Ohm, and it is one of the first batch of BGM stators but with a new LT coil & pickup. When rebuilding the engine, I did change the crank, so if it is machined differently to the previous one, then the flywheel may be higher or lower that before. When rebuilding, I checked the piston clearance, I can't remember the figure, but it was within spec according to Stickys. I also changed the rings.
Sorry this is so long winded, but I'm running out of ideas.
Sorry this is so long winded, but I'm running out of ideas.