honda lead 110 4 stroke starting issue

hi my honda lead is driving me mad.
essentially the bike will start after being charged or on jump leads but without it wont it just turns over.
the battery seems ok as the bike turns over fast like normal.
the voltage on my non calibrated multimeter is bike happy starting with 14v not happy with 13v when running it says 15v-17v im aware these figures are high but i suspect my multimeter is a but optimistic. the battery is about 2 weeks old. and it happens if the engine is hot or cold.
so i am wondering if it is the coil is going bad.
or maybe the voltage regulator?
i have changed the spark plug.
any ideas ?

thanks for your help

 

Hmmm yeah, could be the coil.
Try a new plug again just to be sure

 

To help anyone out there who gets the same problem it was the voltage rectifier it was outputting 15-17v when the jumpleads were on some of the voltage was being dissipated into the charger so it would start, but when the leads were off the full 17v messed up the ecu and stopped it from starting. one terminal on the rectifier was corroded so I replaced it with another ( of a yamaha ytd looked the same and only £10) and now works fine