My recently rebuilt Mc21 has been riding awesome but yesterday when I got to the parking garage, the RPMs sh*t up to almost 10k without moving the throttle. Then I would flare the throttle in hopes it would idle down and it did. Today, I started the bike (on the kick stand so leaning over a bit) and once it warmed up it did it again but would not idle down after I flared the throttle. So, I of course hit the kill switch, motor still running... what?!?? Then I turned the key off, motor still running... WHAT!?!?
To be clear, under normal conditions the bike will NOT run with the key off or kill switch enables. My thought is that the motor was causing detonation from the high RPM and higher compression ratio but nonetheless, what is causing the bike to surge to 10k without moving the throttle??? Even if the throttle position sensor faulted, the cabs need to open up to provide air/fuel to feed it at 10k, right??? If not, then it must be running lean as hell and that scares me.
So I finally got it to stop by sitting on it and standing it upright, off the kick stand and it useless down. Also, it also idled at 3k until I sat on it and stood it up and then it dropped to 1.2k.
This is anything but a simple two stroke motor
