ec200 help !

[chinesegav]

hi wonder if anyone can help me ec200 playing up

whats happing is the bike will run fine when cold anywhere from 15mins to a hour when hot then it will start not wanting to rev neer top end of revs and will then start to lose more revs till it will only give 1/4 throttle but idle fine. I think it is an elec issue can anyone give pointers or common thing to look at

here a list of stuff i done trying to find the issue

1/new spark plug
2/ freash fuel
3/clean air filter
4/new fuel filter
5/cleaned carb
6/look at wiring for a earthing issue
7/check stator
8/ top end rebuild
9/ looked at reeds
10/new spark plug cap and cable

i am thinking it could be the coil or the reg but not sure?

thanks gav