Alright guys I'm getting very close to being able to register my DT2 for street use, Deet rebuilt my key switch/harness (and did one hell of a great job), so now I have everything working but when I apply either front or rear brake the tail light goes dim instead of getting brighter, the battery is 100% charged.  Any thoughts?  Thank you, Tony

Check your earth wires to rear tail light ,  frame , and connection to
main wiring loom , from tail light loom .
Check wattage of tail light bulb .

Thank you, I'll do that.  I did just get a new bulb from Partzilla but that's not saying it's correct, they have sent me wrong parts before...

Bulb should be 1154 maybe you accidentally wired the run light and brake light backwards you can swap the wires on the rear fender and see if that works correctly. Ask me how I know!!

Thanks I'll check bulb, as for wiring I checked to see they are connected correctly color wise and they are... 

Take your lens off and see if both filaments are on in the run position and if one goes out when you apply your brakes maybe your wiring in the front got crossed. Seen it happen before

Verify bulb is correct part number and verify it is inserted correctly, they are suppose to only go in one way but they can be forced to be inserted incorrectly, although as mentioned above your symptoms point to a bad ground in the taillight circuit.

Thanks guys, I have my marching orders. 

So does the brake light work normally without motor running--as you say battery is right up. If it's only doing that with motor running--which i guess is what ya saying--then whats up with the bulb. Is it fitted back to front, not easy to do with offset pins. I've had the odd bulb break a filament then lean over & contact the other filament causing total confusion. Seen the little fitting that the wires attach to where bulb contacts & someone had managed to get that back in half a turn out--also not easy to do. Probably just an earth problem in the end. Don't ya love electrics.

Without the motor running I get nothing when applying brakes, also don't have a tail light and I thought the tail light should be on even if motor is not running...