Me and my mate where out practicing today when we stopped for a breather. my mate kicked his bike up and it started to rev up on its own. he pressed the cutout and its revs dropped slightly then went through the roof! I grabbed a stick and tried to remove the supressor cap (the stick and my gloves where wet) of course I got zapped and could even feel it leaving me thru my boots lol! It still kept on running so we stuck it in 6th and dumped the clutch whilst it was up against a tree. That stalled it. After it had stopped we checked the throttle and it was working fine? Ive heard of this happening before but cant remember what causes it. We didnt fire it up again after, as 30 seconds of full chat was enough for one day lol!

I've had a 2003 315 do similar when riding in streams. The plastic carb top can get distorted allowing moisture in to the slide area. This causes the slide to stick - normally open. When the throttle is tried again after it seems fine. I could tell when mine was sticking as throttle cable felt slack in the twist grip. New plastic top was only a few quid

A guy who was riding there today said it could be moisture. But surely he would have had to rev it for it to stick? Im pretty sure he just fired it up and didnt touch the throttle?

I had the same thing back in 99. Slide stuck open and reved its nuts off. Dad pulled cap off and it stopped, but it siezed. Sounds like a likely theory.

spark plug cap? That thing was running with the cap off! I dont think it was tracking across so it must have been dieseling