Does anyone know anything about the valve sizes on the GSX mills? There was one person here (can't find it in the archives) that had a GSX400 engine... I can't find any info on the web. I'd like to know if the valves are interchangeable. Also like to know if the cylinder spacing is the same.
The GSX400 belongs to the GS400-425-450-500 engine family. The GS250 uses smaller crankcases. This was verified on a different list by someone who compared both engines on his workbench. Knowing that, there's no reason to think a 250cc would share valve sizes with a 400cc.
Which list? Michael Moore's?
Yup. This is the same fellow who successfully transplanted a GS500 head onto a spare GS450 engine (so the pipes would clear the down tubes on the 500's frame).