Not my bike, my friend’s been having problems with his 1998 Fazer spluttering around 3000 rpm, had his carbs apart and cleaned but problem persists.Apparently the problem lies with his HT leads but he can’t afford to get the OE Yamaha just yet so chanced a set from eBay, they are expensive because at the other end they include the…2 round things…coils 
so its not like changing the leads on a car and just popping round to Halfords, I think we’re talking about £160 for a set.
So, he changes them and now tells me of a plastic burning smell and can see a “lightning” kinda spark going from one of his spark plug cap to the engine cover when its running.
Did he buy a knackered set of leads/coil or has he done something obvious wrong? (apart from not buying a new part)
If I remember right, if that happens in a car engine it means the lead is fubar and needs replacing?
I’m not an experienced home mechanic so, please, any advice?