That little bicycle computer I have been using was a lifesaver. However it has a bad habit of resetting itself on occasion. That really throws off my efficiency calculations and I don't like it. I've also been considering adding a tachometer. Not that I need one, but I like to see data! So my bike speedo reset again recently and I was mad enough at it that I bought a TrailTech Vapor computer. It does nearly everything. Speed, tach, and engine temperature! With a backlight so I can see it in the dark! I didn't want to spend the $100 for it.. but bought it anyway mad as I was.
Well, I received it and figured out where to mount it. Pretty much right where the bike speedo was! I like to see my gauges without having to look too far off center. It just turns out this is a good place for me. I made a mounting bracket from some scrap aluminum I had and painted it black. Looks clean!
I had to extend the RPM pickup wire and the temperature sensor. Easy enough to solder another 12" in. I wired the power to the key switch. This make it function like you'd expect it to. The backlight comes on with the key. I don't know why they recommend to wire it always hot. I hooked up all the sensors (wheel pulse, spark plug temperature, RPM wire) and it looked great! However when I started the engine the MPH jumped all over the place. I had this same issue with the bike speedometer but thought it was because it was ungrounded or poor design. I was expecting a speedometer designed for a motorcycle to not be susceptible to electrical engine noise.
After some tech-support and forum messaging the solution is simple: disconnect the tack pickup wire from the computer. It can still pickup the RPM from the general noise (very sensitive!) and it doesn't affect the speed. Now I'm quite happy with it and love to see my RPM and engine temperature. Now, I'm glad I did it and probably should have done it earlier!