My mates 250 will not start. It ran fine when he last run it about 6 weeks ago and then put it in the shed. Carb all cleaned out and fuel getting to the chamber. BUT no spark at the plug, but getting a spark at the end of the HT lead. Changed 2 different caps and 2 different plugs but still no spark at the plug !! Is he missing something ????. Can a weak spark get to the end of the HT lead but struggle to get to the plug ? Any ideas pls. Bob.