I've had a similar problem with mine since I bought it second hand. The problem only ever happens when on a neutral trottle at low revs (i.e. through traffic, built up areas etc.) Similar to the things you've experienced...more of a hiccup than a missfire, like a pop/hiss, and as you say the bike just slightly misses a beat and transmits a slight jolt forward. I'm also aware that I seem to be able to feel it through the trottle, as if when it happens the trottle just jolts in my hand a bit (am i going mad?)!?! And it only does it once...pop/hiss then fine.
When I took my bike to OYB for its 12k service, they tweaked the mixture (I think) and it made it worse...it was almost unridable at low speed through traffic, so when I took it back they changed things back...and it definately improved about 80%...but it still does it now and again, maybe once or twice a ride.
I've learnt to live with it...but I'm hoping that maybe this winter some clever chap will be able to solve it when its serviced (Nelly)?
Any ideas?
[Edited on 14-7-2003 by Harv748]