Much to my local Yamaha dealers dismay, I decided against buying a new WR450 and instead, spent some time and money rebuilding my trusty '03 WR instead. I'm glad I did. I love the stroker WR! It works fantastic in the gnarliest conditions, wheelies without effort over logs and rocks and runs circles around the newer WR. Here's the short list of what has been done to the bike:
Hot Cranks YFZ Stroker Crank (471cc)
Wiseco HC piston (for YFZ450)
OEM Yamaha '07 WR450 cams
Dyna FS programable ignition
'06 YZ405F Forks w/G2R compression and rebound valves.
'06 WR450 triple clamps, digital display, kickstand, and wiring harness.
'07 WR450 footpegs, brake disks, front axle spacer.
'04 electric starter upgrades.
'04 YFZ450 flywheel.
'06 WR transmission, shift fork, and selector upgrades.
'07 YFZ clutch cover (with piston cooling jet) and oil pump.
13-52 gearing w/Michelin trials tire (summer) 14-49 gearing w/Maxxis Desert IT (winter)
I learned so much info about the small differences between the '03 and '06 models and the YFZ that my brain still hurts. There are some small differences (like the can chain buffer bolts) unique to the '03 WR that can cause some real headaches if you aren't aware of them.
Edited by 2grimjim, April 09, 2011 - 02:35 PM.