I've been riding Pauline's 'Storm for the last few days - and I've noticed a misfire/splutter around 3,500-4,000 RPM, usually after using more throttle/revs, backing off, then rolling on the throttle. It clears its throat with more Revs and throttle - and is fine at high revs or large throttle openings.
The bike had manual CCTs about a 1000 miles ago - and had to have the head off as the mechanic had the chain jump some teeth and bend valves (he is a qualified mechanic honest!)
It's had new plugs (iridium), at that 1,000 mile point, a very recent new battery and reg/rec. the bike has a K&N - but when I looked at the old plugs they weren't obviously weak.
Soooo - any thoughts? Anything obvious/known failure points that I need to check? (Do coils fail, any diaphragms fail?)
I can ride through it, but its Pauline's bike - and I need it to run right and be smooth for her to gain experience safely....