I think its a 5/8ths size - i haven't done mine i just know that a standard size won't fit.
I then plunged for my "fits bikes" plug spanner only to reallise it stiil lived under the seat of my old ZXR.

I'm sure if you ask at Halfrauds for a 5/8ths it'll fit - maybe suggest its for a bike?

Sure someone will come and say similar .....

thanks guy's, this is a nightmare!

I've just spent the last hour trying to remove the 5/8 spark plug socket from the plug hole (didn't read the last post in time)! It's out at last, panniced for a while.

I'll machine it down as small as possible tomorrow and start again. Glad I didn't start on number 6 as I'd have had to remove the engine I think.

Why the hell make the dam hole tapper at the bottom!

Cheers,

Richard.

find someone with a jap sports bike......