The two bench grinders I have are not suitable, one has the correct diameter shaft but the flywheel bottoms on the main body of the grinder, the other bench grinder has a shaft whish it too large.
I reverted to the power drill method, this time I fitted a long pipe to the Seagulls inlet port to ensure a supply of clean air.
Note, I always provide lots of lubricant to the motot before running it up with the power drill, there is a bonus to doing the rotation this way as the pistion compression comes up really well.

Thanks for the advice guys,