The flywheel will be best thing to start with. The rear tire will help but that 450 is a beast and the throttle is so touchy when your in the woods. I rode mine for three months before I started making changes. I wanted to find out what I hated about the bike before I changed it. Now I know what I hate about it and more importantly I can tell what each change I make to the bike does.
Most of the changes I have done have been improvements but a few where not so those brand new parts just came off. LOL
The Cyrca 1 1/8 clamps don't bolt up right and the aluminum bar rides tight on the brake cable. If you have a good fall I will shear the line right off. You need a set of clamps that are made for the taper in your bars. I can't remember which ones I have now but I can let you know next week when I get my bike back. Maybe Cyra makes the right clamps that will get everything in the right place but the set I have don't. I'll sell my set to you for $100 bucks. LOL
Another bad change was going up to a 52 tooth rear. It helped with the stalling but put too much torque to the rear. It broke loose even worse which wasn't worth the offset.
Another bad thing was water wetter. I flushed my radiator and put straight water with water wetter in it because it makes it run cooler. Only problem was the boil temp went way down and the bike would boil over after 45 seconds of sitting at idle. I just run straight Honda
antifreeze and the problem has gone away.
Along the lines of the over heating, I forgot to mention in the PM's I put a set of Crycra Power Flow plastics on the bike. The guys from Cycra
did extensive testing with the YZ's and thier radiator shrouds cool the motor 8 to 10 degrees. I went with the full set. I figured for running slow tight stuff any little bit will help the bike.
Have fun with it. Great bike with a few cheap adjustments.