First off, my OL had a 650 yammy for about a year and put 35 miles on it because it was just not up to the job. It was traded in for an America in '03, and the America is a keeper.
Next, the America engine is near 50% bigger and, as Racer brown used to say, "The only substitute for cubic inches is more cubic inches".
The America handles and goes a lot better and is much more reliable.
Borrow (don't waste money buying one) a service manual for the 650 and look at how much is involved in changing the rear tire. Every 15 - 20 Kmiles, you will have to disassemble half the bike.
