Anybody know what conditions trip a check engine light on a non-emissions, carbureted pre-CAN bike?

I've never seen mine light up and I'm debating if I should bother wiring it up with my custom setup. It Will take some diodes and effort that I'm not sure will have any benefit.

 

 

I've wondered this same thing.

Mine came on a couple of times shortly after my engine build, while I was chasing a noise in the cam chest. The Check Engine light would come on if the engine had been running for a bit. I found a bad cam chain (which I had idiotically reused). Once fixed, the light never came back on again.

 

Sounds like building the circuit to make this work on my setup is a wasted effort. I'll seal off the lead (black w/ yellow stripe) and make a note to revisit whenever I do the Thunderheart ignition.