An easy fix for signal "fast" flashing w/ aftermarket blinkers
I had to replace my rear KLR signals, and I chose smaller aftermarket ones made by K and S. 'Course, the flasher unit doesn't detect them since they draw less amperage than the stock ones. On the KLR the blinkers just stay lit. on most other bikes they fast flash in this scenario.
Rather than replace the flasher unit, I got some NAPA 35W halogen bulbs made my Wagner / Federal Mogul (sorry, no part number available, I already installed them) that have the same bayonet mount as the stock bulbs. I replaced the front bulbs with the NAPA ones. Now the front signals draw enough amperage that they actually flash normally by themselves; you can add any kind of rear signal including an LED and they will continue to maintain the correct flash rate.
This should work on any bike with front signals that aren't dual filament.
In years past, I used it on a Suzuki Bandit, which shares signals with the DRZ400, so it'll work on those bikes, too.