If you are using the stock 40mm head with the BBK then compression will be much higher than it was . Many opt for adding a secondary base gasket to lower compression a hair . Does it have the stock CDI ? Many aftermarket performance CDIs have advanced timing and some have reported it was not as easy to start as before .
Check the valve clearances as too tight can make it hard to start , stall once warm and in extreme cases no start at all . Many how to videos on You Tube .
I also had this kit and was impressed with the craftsmanship and performance . I used a 95 main jet with airbox and stock exhaust . I used 5g rollers instead of 8g that it came with since it is hilly here and Im a 200 lb guy .
A buddy used that BBK with a big valve head on the top of this page along with a 24mm carb , Uni and performance exhaust
http://www.scrappydogscooters.com/13...rformance.html
With a new BBK I would put on a new belt too