OK, I'm gonna make a new thread in the projects and builds section. For now though I have been experimenting with the arduino rpm measurement. It's sort of working but I don't think it's very accurate. There is mad emi coming off the engine and I think I'm counting stray pulses. My bike is positive ground, so I have the positive SLA terminal going to ground (one of the engine studs), and the negative going to the white wire through an N4001 diode. There is a second N4001 diode that goes to pin 2 of the arduino, which is tied to interrupt on the falling edge and increments a counter when it is pulled low. The internal pullup (~5k ohms) holds the pin high otherwise. Theory is when the engine volts goes low enough to charge the battery it will also pull that pin low. I think this may not be the best way to do it though since I have the two diodes in parallel they have to match pretty precisely to work right. When I first hooked this up I was reading 7000 rpm at idle, which is obviously wrong. I put a 100 nF capacitor from pin 2 to ground and then it dropped to about 2900. That sounds closer, but still high. Any idea what these things usually idle at? It's a 80cc two stroke. Anyway it might be good enough I just wanted a rough indication. I'll start working on the speedometer next then the lights and controls. I'll start a new thread once I have photos.