I have a World Karting manual from 1990 and no mention of Mc's or West bends. I know Mc was making chain saws later on but must have dropped out of the kart business. It seems like Briggs was the 4 cycle king and 2 cycles were mostly foreign engines, Komet, Parilli, Yamaha and others. And of course everything went hi tech with water cooling, gear boxes and computers. My pockets weren't that deep to get into the racing aspect of Karting. I did race my Bug with the Mc 101 and it was competitive till somebody ran me over. Time to look for a new hobby. By the way my 21/2 hp Clinton was only $25 on electronics row which was called that one time but was actually Canal St. in NYC, were you could buy almost anything electrical or mechanical including tools at good prices. Fake rolexes were always on sale there too.