RE: Engine size comparison (SPE26 & G20EI)
OK, these are the dimensions that I've taken. The width from muffler to carb excluding velocity stack is 158mm for the G20 and 155mm for the SPE using the spe muffler for both( bolt head included) and about the same if the standard muffler is used for the G20. Height from shaft centre to plug is 130mm for the SPE and about 128mm for the G20. The SPE has a slanted plug so there might be more to cut. Cylinder head dimensions 55mmx70mm for the G20 and 50x60mm for the SPE but then again allowance musrt be given for the slanted plug.The velocity stack measures 25mm tall.
Hope this helps