I've got the same problem 
Bike has an aftermarket can and pipes, my regular mechanic suggests it could be down to this.
So far I have done the following (some just because it needed it):
Still to do:
Bike has an aftermarket can and pipes, my regular mechanic suggests it could be down to this.So far I have done the following (some just because it needed it):
- Oil and Filter change
- New Spark Plugs
- New Spark Pug Caps
- Brake Fluid change
- Carbs Balanced
- Checked air filter - looks pretty good still
- TPS Checked and all good
- Replace Coils
Still to do:
- Regulator/Rectifier