yfz 450 and yz450f motors

[stephiesjeffy]

Ok everyone we all want more power and speed out of our yfz's but I have a question for those who know something about this.
By Yamaha standards the yfz450's hp rate is 39 hp stock and the yz450f is rated at 55 stock. My question is. This is the same motor in these machines I would like 55 hp pumping out of my yzf just like all of you would what kind of modification do we got to do to get the same hp rate as the yz450f someone please post something about this I think it is weird but hey I'm just wanting more bang for my buck just all of you. wwe all want the best mods for our quads.

[Hozed]

i dont think the dirtbike pumps out that much power... as far i know the only difference between the 2 is the timing and 11cc's of displacment.
i think.

[EvilJester400EX]

My guess is that the only reason that the dirtbike engine pumps out more hp on the dyno's is because of the weight. Timing and compression couldn't make that much difference, I don't think so at least. It's super easy to punch top HP numbers from the YFZ engine, cam mod and a pipe, you're already around 54hp, put a high compression piston (13:1 or 14:1) and you're roughly around 58hp.

[nhyfzrider]

the yz450f has a free flowing exhaust from the factory, and the yfz450 is severly plugged up. pipe up the yfz, retard the cam, and your looking at mid to high 40's. i'd love to find a yz450f motor to throw in my yfz.

[Hozed]

Originally posted by EvilJester400EX
My guess is that the only reason that the dirtbike engine pumps out more hp on the dyno's is because of the weight. Timing and compression couldn't make that much difference, I don't think so at least. It's super easy to punch top HP numbers from the YFZ engine, cam mod and a pipe, you're already around 54hp, put a high compression piston (13:1 or 14:1) and you're roughly around 58hp.


lol!!! those are some high numbers there son!!!
there is no way a yfz gets near 54HP with a pipe and the cammod... maybe around 45... but thats about it.

as for throwing a yz450f motor in the yfz... id love too... but only if it was an 04, they come with 4 gears instead of 5.. i think it would be neat to try... other than that they are pretty much the same.

[bradley300]

the yfz has the WR motor, not the YZF, i beleive there are some other significant differences in the two as the WR is a smoother woods motor. and 54 HP from a yzf is totally beleiveable

[Hozed]

the wr motor and yfz motor are the same... just timing and cam i belive. (i had forgot about the cam before hand.)
and 54 HP can happen... but not with just a pipe and cammod...

[EvilJester400EX]

Originally posted by Hozed
the wr motor and yfz motor are the same... just timing and cam i belive. (i had forgot about the cam before hand.)
and 54 HP can happen... but not with just a pipe and cammod...

GYTR full aluminum exhaust, cam mod, and a 13:1 GYTR piston. Dyno'd at 58.6hp. ;)

[Crazy Honda]

All you need is a crank out of a 04 wr 450 and the yzf piston 13.5:1 and the yz cams then you have the same motor as in the bikes. the 04 wr crank is 1.44mm larger and comes with the rod but the wristpin is smaller so you need the dirt bike piston. I checked around and found all parts from a local dealer was 600.00 with gaskets not bad for a drop in stroker kit with cams!!:eek2: :eek: :D P.S. this puts you at a true 449cc

[Hozed]

Originally posted by EvilJester400EX
GYTR full aluminum exhaust, cam mod, and a 13:1 GYTR piston. Dyno'd at 58.6hp. ;)


i dont believe it... show me the slip then i will...
doug gust's z450 is one of the top power makers in gnc... he has a little over 50... if thats the case than all those yfz's should be running up near 65-70 will all the motor work they got done.

[EvilJester400EX]

Originally posted by Hozed
i dont believe it... show me the slip then i will...
doug gust's z450 is one of the top power makers in gnc... he has a little over 50... if thats the case than all those yfz's should be running up near 65-70 will all the motor work they got done.

It's not my slips, but my mechanics YFZ, mine is set up exactly like it, but I'll try and get them for you.

[Hozed]

i just dont see how a pipe, timing change and a piston can produce 20HP...