450 not the same in the quad as the bike

[PHIL_B54]

maybe someone has already notice this but looking at the yamaha specs between the new 450 quad and the 450 dirtbike it looks like they detuned the quad version

quad:
Engine
Type 439cc, 4-Stroke Single, Liquid Cooled w/ Fan, Titanium 5-Valve DOHC
Bore x Stroke 95mm x 62mm
Compression Ratio 11.9:1

dirtbike:
Engine
Type 449cc, liquid-cooled, 5-valve, DOHC, 4-stroke w/titanium valves
Bore x Stroke 95 x 63.4mm
Compression Ratio 12.5:1

[GETSOME]

The difference in the compression ratio and the displacement is the result of using the WR motorcycle bottom end which has a slightly shorter stroke. They did this to borrow the electric start on the WR which the YZ did not have.

[airheadedduner]

GNC 250 pro class limit is 440cc could be why, well thats what I think anyway. A quad puts a lot more stress on a motor too, much more rubber on the ground and weight. Thoose arn't the only differences, the tranny will be quite different. They kinda crossed the yzf and wr motors for this one. It think I heard it has WR cams. Look in the other threads if you want more info about the difffences.

[PHIL_B54]

i thought that i did compair it to the WR, so i take it other people noticed it too

[TheRedRebel17]

Originally posted by airheadedduner
[B]It think I heard it has WR cams. [B]

i'm pretty sure it has a YFZ intake cam and WR exhaust cam.

[Dan_Guetter]

theres a write up on ******** that talks about the engine. the tranny is more beefy then the WR and the YZF. the engine was destroked to 439cc to make up for the AMA 440cc limit. you can however import a YZF crank and top end to get the full 450cc without going to engine builders. this thing is a dream come true to most of us!