Well ATV Action hasn't riden it yet either but there is some new info in this issue

They say that both Exhaust & intake cams are the same as the YZ-F motorcycle but the exhaust cam is retarded 1 tooth for more tractable power. Advance the cam 1 tooth & you have YZ-F power.
No linkage on the shift lever.
FCR style carb instead of CV carb.
Combustion chamber is identical to YZ-F
Stroke is rediced 1.4 mm to get under 440cc limit (I think the limit has been changed to 450cc's will the 05 YFZ be 450cc's??)
Stronger piston than the YZ-F (stronger wrist pin)
Cylinder is all aluminum (no steel sleeve) it's ceramic composite coated like the R1 & R6 street bikes (Lighter & better cooling).
11.9:1 compression (uses 93 octane)
Clutch plates are 1.6mm thick compaired to 1.2mm thick on the YZ-F
Quick access magnisium clutch cover.
Close ratio 5 speed suited more for closed course than trails.
60% of the testing was on MX tracks & 40% was in trails & dunes.
Front & rear shocks are piggyback rezzys & have rebound, compression & threaded preload (a first on mass prouduced quads!).
Rear Dunlops are a new design unique to the YFZ450, front Dunlops are patterened after the Raptor front tires but have stiffer side walls.
Adding the kickstarter & removing the electric starter & electronics save as much as 15 LBS
There is a pic of the kickstarter & GYT-R heel plates that clear the kick starter & allow rearward kick.
Auto decompression will make kick starting easier.
GYT-R also has Nerfs
Cast aluminum swing arm is hollow for light weight & has an anti squat bend
Rear shock is moved forward as much as possible to keep weight centered.
Chain adjustment is cam type.
Stock exhaust is 82db & is green sticker legal in Calif!!!!
Yamaha says that by removing the lid, putting on the GYT-R carbon fiber slip on & rejetting adds 15% more HP!!
Wider a arms, wider axles, skid plates, a arm protectors, shifter, brake pedal, front bumper, grab bar, heel guards, nerf bars & other goodies will be availible from GYT-R
The sub frame is made of cast aluminum using Yamahas exclusive CF casting technology & is designed to heep heat away from air box.
Well that's about it, ATV action did not mention any HP numbers.

My dealer says the quads have beem shipped to the distribution centers & they expect them on the showroom soon (next week).
He said they are getting 1 blue YFZ, do you think it'll go for sticker price?? LOL!!

 

thanks again