Witchcraft, voodoo, global warming? Odd ATC issue.
I had something really weird happen while taking my 85 250R out for a spin the other day. I bought this trike back in 85 and have owned it ever since. It is stock with exception of the Uni air filter. I am running Maxima Formula K2 at around 32:1 or 40:1, spark plug is an NGK BR8EV gapped according to spec(stock is BR9ES). I don't remember the main jet size, but I am running leaner main jet than stock 142 size (altitude is about 4500 ft). I am running the stock pilot jet with the needle on the 1st groove, and Boyeesen reeds (spelling?) It runs great. Like I said, I took it for a spin to run some gas through it. On a stretch of dirt road, I briefly ran it wide open. When I let off the throttle, it remained revving almost wide open. I thought the carb slide was stuck open but it wasn't. I hit the kill switch and it stayed running! I reached above the head and pulled the plug wire and it STAYED RUNNING! I thought it was going to blow up. I finally stalled it with the clutch. I let it set a while, started it, and all was fine. I rode it home at a pretty calm speed and I checked the plug, it looked fine, except for being a little wet. Now it does have a recent top end with very few hours on it. I run 90 octane, because it is all we have where I live. The manual recommends 91. Has anyone ever heard of something like this? What could have caused it. It could not have a hot spot due to carbon build up on the head or piston. I doubt it was a fuel/octane issue since it was fresh fuel. The only thing I can come up with is the spark plug. Maybe it got too hot and was igniting fuel despite the kill switch being off AND the spark plug cable being disconnected? I am at a loss. Thanks for any ideas.