The first generation Pampera (released approx 1996) had a smaller radiator than the later models. These first Pamperas also had the "trials gearbox" , later models had some gears with different ratios.
I suspect that you have a ground fault in your lighting system. Disconnect all of your lighting, then take the bike for a ride. If everything works as it should you will know that your issue is with some part of your lighting circuit.