I finally got around to putting a larger jet in the 50cc scooter and thought while I'm at it I'll put in one of the new spark plugs I bought a while back ... NKG CR7HSA ... the scooter would not start ... I checked the usual things and no spark. After some trouble shooting and confirming the coil was getting enough current to fire, a friend mentioned he'd once gotten a bad new spark plug. I got one from a scooter that ran and put it in the 50cc and it started right up. So I'm looking now at the brand new spark plug wondering WTH ?
