Thanks for the replies
With the wood trick, what would I be listening for? Mind you, the idea of riding along with my head on one side and a piece of 2x4 sticking through my helmet into my ear is quite an amusing one - as long as there are no speed bumps!
On a more serious note, this is proving tricky to analyse as idling and higher-rev riding is fine. Sigh.
Where does anyone suggest I should start first (and no reg-rec comments just yet
)? I'm thinking replace both HT leads and sparks and see what happens? It's just bizzare trying to work out what would cause it to only happen under low-rev acceleration.
Al.