if your pushing it in nuetral, and there is drag, then I wouldn't think the crank, or top end has anything to do with that.

Since being in nuetral means the wheel is not driving the crank/piston, but is turning things in the gearbox, I would wonder what is happening in the gearbox.

Did you check your gear oil before running it? Was there any in there? How much? How new?

When you try to kick over the bike, can you not move the kick starter, or does it not actually fire (but the kick started goes through the motions).

I would drop your pipes, look up in the exhaust ports to inspect your top end and check your gear box.
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Charles Gallant