Ty Wouldn't Stop

[aardy]

I lowered the needle jet to improve the high speed running on my '84 mono and it worked. However after trying it out I was comming back when the engine wouldn't slow down with the throttle so I hit the kill button and nothing. I pulled in the clutch and coasted to a stop with the engine reving very fast. I turned off the petrol then gritted my teeth and pulled off the spark plug lead. Still nothing - the engine kept reving very fast. I had no idea what to do after that. Then after a few seconds smoke came from around the top of the engine or under the tank or somewhere and after another couple of seconds it died alltogether. Now there is no spark. Anyone any ideas.

PS Trials bikes are very light when they are going but after pushing one 2 miles or so well you can imagine!!!!!

[mjfriesen]

sounds like it was running way too lean and over heated, causing the bike to "diesel", i.e. run even without the benefit of a spark. I had this happen to me once when i was chasing a friend on an atv on trails he knew very well. my old bike did not like going ~45 mph continuously. it actually got so hot i could only stop it by shutting off the gas - should have thought to block the exhaust, but oh well!

It may be that lowering the needle is causing it to run lean and over heat, or maybe the needle is a coincidence. i would check it out, and see if it is dangerously lean.

hope you sort it out!

[diggin4s]

Typically a lot of oil has condensated on the bottom of the crankcase(more fuel), waiting to get heated & vapoured during this diesel effect, may of minimized damage, as suggested a glove or boot on the exhaust will shut it down the best, unless your system is very leaky.

Thinking about covering the exhaust when its reving & realizing killing the spark is not the answer often comes from a bystander with no vested interest in the bike.

Little chance of this happening on a 4 stroke, no residual oil etc. in mixing/combustion chamber.