Welcome aboard
I'm assuming this is a Transistor ignition engine.If so take a look at this post,
http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=8&t=84The plug caps can cause this problem but then so can un-serviced/dirty carbs,
http://globalcxglvtwins.hostingdelivered.com/viewforum.php?f=19Also join Chopper Charle's forum in the US as there's a lot of traffic on there and of course closer for you should you need links for parts and there are many Canadian owners who may even be near you to help,
http://choppercharles.com/cs/forums/