Hey beachcruiser -- scratching my head here ?? Doesn't seem like it would matter where the engine is located as far as top speed. OK - I am just getting back into Mbs myself -- is this a chain, belt or friction drive ? With a friction drive - I don't see where location could make a difference in either contact to tire or top speed.. With a chain or belt drive - location of engine - could make a slight difference. Happy Riding from - Mountainman
Maybe your alignment became much better. Good alignment means less resistance. Less resistance means more speed!
Also moving your engine changed the angle of your carby. Maybe that has something to do with it too.