Yamaha F30 no spark on middle cylinder

[KennyBradley]

Hi,<br /><br />I'm looking for some advice on this engine. Looks like I have an intermittent problem with the spark on the middle cylinder.<br /><br />I would be very gratefull if someone could advise on how to diagnose the problem.<br /><br />I've tried swapping coils and checking the condition of the wiring back to the CDi without success. I presume the charge coil and power coils serve all 3 cylinders so they shouldn't be the problem?????? So the problem must with the CDI unit or downstream from there??????<br /><br />Any help would be much appriciated.<br /><br />Cheers Kenny