The most likely fault is a failed ignition module.
There are no points on this engine.
What is referred to as the 'condenser' by the last contributor is - I think - the module concerned. It's mounted on the throttle control assembly bracket. Bad news - I have no idea where to get a new replacement. Good news is - there is an after-market alternative that costs about £5.
I have them in stock, but it's NOT a guaranteed fix - the fault could be in the coil itself. I'm still lookng for a supplier - will post back here if I succeed in finding one.
phil_saunders(a)bigfoot.com
Phil Saunders
March 2010