Thanks for the replies gents. The connection to the 10-1 seems to make sense as during the last annual we noticed certain features that seemed more akin to the 10-2 (common in Chipmunks here in Oz) than the normal Series 1 engines. I’ve read that the 10-1 and 10-2 only differed in the 10-2 having the splined crankshaft. I actually have a splined crank in mine, and have bronze heads.

What sort of differences were made for the 10-1 from the Series 1 engines? I’m assuming the changes were made as an improvement?

Thanks again for the assistance so far.

Cheers,
Matt