Broken pick-up wires

[Steptoe]

some symptoms to look for,,

vibrations that aren,t normal,,
unusually sluggish off the mark,
intermittent loss of spark under power or decelleration
just plain won,t fire
anything out of the norm for your bike

http://www.youtube.com/watch?v=ywOGlDri-q8

not my greatest work, but it might help someone