Let's see, R90s, got it.
First things first, you will want the Kisan SM-1. This relay provides the running lights and turn signal "Brake Flash" functions, as well as creating a two-channel system. The last part is especially important since you have a single turn signal dash indicator. The SM-1 will force one side or the other to blink, rather than experiencing an "all four flash" situation as previously mentioned. Be sure to hook up all required wires in the SM-1 (Scotchlok connectors are included).
If you have any doubts or questions about the SM-1 or Tailblazer and your bike, call Kisan and talk to Andy - very friendly, knowledgeable, and helpful.
It'd be nice to have whatever info you get from Andy posted here for others if you do call.
Motoelekt.com sells the Beacon I LED replacement panel, which you could use for brighter running and stop lights at the tail. My buddy had one of these on his /5, and it was great. You could (probably) also wire in a Kisan 100HD Tailblazer here to provide stop modulation with the LED replacement board (***untested or verified, but theoretically should work***).
If you don't want to go with the Beacon I, you can get the Kisan 20W-D Tailblazer bulb, which is an electronically controlled Halogen 1157 replacement bulb for the stock socket and reflector. This will give you plug-n-play stop light modulation.
Beyond that, 1156-x18-Ts or 1156-x45-Ts from superbrightleds.com all around on the turn signal bulbs, and you will be rocking.
Plenty of choices for license plate add-ons (like my Lite-Blazer, or the other products mentioned previously). But the stuff above would get you started.
Current: 93 R100GS, 03 XR650R
Prior: 73 CB350, 77 R100/7, 83 R100RT, 04 XR650L
I love every motorcycle I've owned and even some that I haven't.
ignatz72 screwed with this post 01-24-2012 at 07:37 AM