Q How do I diagnose a poor spark problem?
My Honda NT650V runs well, but occasionally the engine starts to run really roughly, almost like a single, and the rev counter drops to zero. If I turn the ignition off for about 20 seconds and then restart, it then runs fine for a few days before it does it again. Eddie Swaep, email
A Answered by Scott Bullett, Doble Motorcycles It seems like it’s an electrical problem that starts to occur once the bike has warmed up. Here’s a way of narrowing down on the possible cause that works on any bike. Have a spare spark plug in your pocket and when it starts to play up, stall the bike with the ignition still on. Your bike has four HT leads, two on the front, two on the rear, so try to get a lead off each cylinder in turn and put the spare plug in, letting it rest against the engine for an earth. Crank the engine on the start button and see if you have got a spark on both cylinders. I suspect one will be dead and it is more than likely a crank sensor that is behind the clutch cover on your bike.