I have a Raptor Shiftlight, its great and easy to install
http://www.raptorperformance.com/
(From Raptor's Website)
Everything needed to connect the Raptor rev light is located on the back of the existing, on-board tachometer.
1. Remove the seat.
2. Disconnect the negative terminal on the battery. - Important!
3. Remove the top cover.
4. Remove the air filter case cover.
5. Remove the air filter.
6. Take time to protect the carburetor intakes. - Important!
7. Look under the existing instrument panel and unscrew the two mounting bolts.
8. Turn the instrument panel over and unbolt the mounting bracket from the instrument panel (two nuts). You are trying to access the back of the existing tachometer.
9. Place your inline fuse on the red wire. - Important
10. On the back of the existing tachometer you have three terminals. On the 2004 models the black is your needed ground wire. The Gray/yellow is your needed tach wire, and the brown is your needed switched 12 volts connection. Take time to make sure none of the wires are touching each other after you are done with your connections.
11.Set the light for 2 cylinder mode
12. Before you start back out, you can test your work for the most part, by simply connecting the ground terminal and turning the ignition key to the "on" position. It should perform exactly as the instructions say it will. You might want to determine how many flashes you can expect ahead of may time to be ready for that.
13. Once that has been accomplished, you back out in inverse order of the way you came in, with the exception of the negative battery cable.