Here's an OEM parts look up with exploded diagrams of the the whole motor. Just start making a list of every single little part that you do not have. It's gonna be a big list. Brackets, springs, bolts, washers, bearings, gears, clutch parts, covers, kicker parts, etc. I'll bet you end up spending $2,000 getting your $600 Banshee rideable.
http://www.bikebandit.com/houseofmotorcycles/2000-yamaha-banshee-350-yfz350m/o/m145962