The 2000 Avanti's had a couple of problems that were fixed in 2001. 1, they used the same Del'Orto carb. that was used on the Garelli's but the jet was too small (I think it was a 50) for the more powerful Avanti motor, so they would soft seize in colder climates, so in 2001 they went to a Pacco carb. with a 54 jet and it also has a fuel mixture adjustment screw like the Mikuni carbs. so you can adjust the mixture when the temp. changes. 2, In 2001 they changed the pipe to a Bi-Turbo type with an expansion chamber, it helped mid range and top end.
Also, the Mont is only a single speed 20-25MPH tops, the 2 speed Autopower, Kobra and SuperSport will top out at 35-40MPH. You are better off looking for a 2001 or later 2 speed Avanti.