Commando carburation problem (update)

Thanks for some really good replies to my post of last week.
I've had another look at the problem, and notice the Pazon ignition I recently fitted wasn't correctly earthed, which probably resulted in a weak spark on the right cylinder.
After earthing both the engine and ignition last night and a 30 miles run today (to the Calne Bike Day) the plug colour is now a more healthy colour and not sooty black. Fingers crossed... the problem is fixed.
Thanks again to all who replied for some thoughtful responses. This is a good forum! Simon

not the same issue but I had a bad termina on the ground cable to my power arc which left starting in a failed state last week. These electronic ignitions are suseptible to bad grounds!