OK, if you are wanting to run at fifth gear pinned at night, purchase the high dollar units and stay out of the hospital. However, if your race is more technical at slower speeds, here is what you do:
1. Purchase the 75 Watt coil and install it.
2. Purchase a battery for an electric start KTM 525. The battery gives you constant voltage regardless of RPM, so you have light at idle. You can also run true 75 watt power lights (preferably two 35 watts just in case one burns out.)
3. Purchase a Moose voltage regulator (the lighting coil will put out AC voltage, so you will need to convert this to DC voltage with a regulator. A regulator has four wires, two in and two out. If you purchase a rectifier (two wire), this will not charge your battery, as it is AC voltage, so just controls voltage spikes.) With the regulater, you will keep the battery charged at higher RPMS.
4. Purchase two Mountain Bike Helmet Lights. Attach these to your helmet. I'm not sure if you have ever ridden at night before, but the headlight follows the front wheel, but sometimes you need to see to the right or left, especially in the corners. The helmet lights will follow your head, and can keep you off your head. (this is probably a good thing to do even if you opt for the high dollar lights)
I had trouble finding a lighting coil that would fit under my flywheel, so I had to wind my own lighting coil using an old stator for my core. 340 wraps with 20 gauge magnet wire, and I have lights. I don't race at night, but rather just to get back to the truck if we stay out to late, so don't need mine to be as bright as I would if I raced at night.
Let us know what you decide.
Rick