Hi Robert
I suspect the 650 starter motor will not fit for two reasons, firstly the engines are not identical with the 500 being air cooled with a cam belt and the 650 BMW/aprilia engine is water cooled and has a cam chain.
I have a BMW G650GS so I can take some dims for you and I have the Haynes manual which will have pics etc, let me know what I can do..
500 to 650 is a 30% increase so I don’t think they would have used the 500 one on the 650s, but I could be wrong.
A couple of potential sources:
Diesel Dave in West Yorkshire, Bynnzi knows him, He deals in the Armstrong and Harley Davidson military bikes that used the air cooled 350 and 500 engines.
MT Riders group who ride the above bikes http://mtridersclub.co.uk
They have Sales and Wanted sections on their forum.
CCM used the 600cc version of the aircooled engine in some of their R30 Supermotos. The 600 engine was a direct swap for the 350/500 so maybe you’ll get lucky. CCM also used a Suzuki engine in the R30 so beware.
The above reminds me of when I asked my Mum what a couple was and she said “Oh two or three” no wonder my Dad divorced her:)
Hope this helps.
Brian
