A local chap gave me a Bosch r6 spark plug which has the smaller hex body and thinner insulation. The fact that the central electrode protrudes so much however, gives me reservations about the combustion process.
Still having problems with oil burning. I have had the head off about six times trying to solve the problem. A standard size piston in a standard sized bored liner must be right. However oil is finding it's way passed the rings. I conclude that the Australian JP pistons need some fettling in the ring grooves.
Just as well I took the head and barrel off this time as the small end bush has moved in the conrod.
Good photo of Derek Minter standing beside Steve Lancefield the famous Manx Norton tuner.