Thanks Rob. Those measurements don't seem to tell me why the GXV140 and GXV160 use spacers under the ignition module while the GXV120 does not. That is a mystery still to be solved. It also sounds as if a GXV140 or GXV160 aluminium flywheel might fit on a GXV120, in place of the cast iron one. I doubt it would kick back, because the GXV140 doesn't kick back. However the GXV120 has a plastic fan that sits on top of the cast iron flywheel, while the other two have an integral aluminium cooling fan, so there may be issues with the starter cup. Not something I'm going to try in the short term, because I don't have an aluminium Honda flywheel anyway.
