WR 450 Dyno run.

Has anyone done any dyno runs on their wr450's. I reciently bought a 04 wr450 and Yamaha says they crank out 60 horse. I did the airbox mod and uncorked the exhaust and wound up at 33.9. Did the yz cam and then wound up at 35.3. Which is still way low from what Yamaha says I should have. The baseline showed 26.5 hp. I just would like to know if this is average or what?

42 hp for the WR450 and 47 hp for the YZ450 is more or less what dyno results I have heard at the rear wheel. Each Dyno is different and calibration and set up will vary. Your knobby tires will also throw it off compared to a super moto street tire set up. The numbers are not as important as the difference you gain from the changes on the same dyno under the same conditions. :thumbsup:

Saw an interview with Decoster not to long ago. He was saying that we are fast approaching HP levels that are to much for anyone. He says after we hit 55 HP no one out there will be able to use it. Probably a few years down the road but ya never know.

That's 60hp at the crank.....you'll see less at the rear wheel. And it'll be lower than actual if you had the knobby on.....can you say wheel hop?

there is no way a wr450 or a yz450 is 60hp at the crank.

but it would be fun.

You calling Yamaha a liar???? :thumbsup:

A guy I know who owns a bike shop built an engine that makes 58Hp at the rear wheel. 426 bored to 450, 13.5:1, methanol, trick head and hot cams is what it takes to get those numbers.

I bet he has trany problems :thumbsup:

Can you get "tranny problems" done on medicare??lol

Some complex procedures those!

I just wanted to just get some real world numbers, not cause a war. Just a comparison. Some folks made a valid point that a bigger number is more which is good... but everyone had to start out somewhere didn't they. Just what you have seen, personally with a dyno not with some brothers uncle that can ride some bikes on the back wheel for a long time with the good bikes and not so long for the not so good bikes.

42bhp for wr450 seems fear on the wheel. My old 426 put 42bhp after some head tunning. It was 38bhp before that. However as stated before numbers are not important - it's the difference after the mods. Here is some more info.

Lid removed +1 hp

Seat remove +1 hp more

Cold byke -2/3 hp

Head mod descriped at http://www.mototuneusa.com/ +4 bhp

BTW changin the stock air filter to twin air did not do any hp gain!

I bet he has trany problems

It's a flat track bike. I guess the trials tyre that they have to run on the rear doesn't get enough traction in the dirt to stress it too much.

I've got a theory about the YZ/WR gearbox dramas. After fixing mine which was trashed, I believe that the dogs round out due to missed shifts, which causes the gears to ramp out into 'false nuetrals'. I think the damage is done when they re-engage, normally under full throttle. Unless someone has a baby video camera in there, we'll never know. It's a case of what came first, the chicken or the egg? I could, and probably am wrong, but its worth thinking about.

Sabin, what did you use to build up the floor of the port? I did some flow testing on my ZXR a while ago and got great results on the flow bench, but didnt go ahead with it due to hearing bad stories of the filler cracking and jamming the throttle open. I didnt get higher peak flow, but the flow at partial valve lift was much improved.

"jamming the throttle open" I do not anderstand :thumbsup:. What we did was intake ports... before the valves ...

Anyway we use JB weld as described in the article. We did 4 engines - one CRF, one WR426, one suzuki DR650 and one NX650 Dominator all with great results! No JB failare so far! I checked the WR after about 5000km and no problems till now.

Sabin, This is what happened to a person who did this mod to a Pajero offroad racer. I know it's very unlikely, but still possible. The devcon or whatever else you use to build up the floor of the port before the valve cracks. Most of the cracked material enters the engine wia the intake valve. Due to the pulses that occour in the inlet track when the valve closes, a portion of the devcon is forced back to the carby jamming the slide open. I know in our application any putty getting stuck under a small Ti valve would end it instant engine failure, which would prevent anything bad from happening. With the Pajero, the driver lifted the throttle for the next corner, but she just kept pulling :thumbsup: I know people are going to say 'just hit the kill switch', but the time it take to do that when you are already cutting it fine braking at the end of a straight would lead to disaster.

my 2 cents worth


I bet he has trany problems :thumbsup:

why do you say this?

I have a 400 with 426 jug bored out to 444 with 13:1 piston, should I be worried about the transmission failing?

Well maybe not if Hamish teory is right...

put on a supercharger and you 85, put on a edelbrock nitrous kit and you get 115, strengthen the gearbox run the strongest chain you can find put in 8kg springs and you got a real head turner at the drags. 8sec head turner.

ride hard and life fast :thumbsup:

I have a 400 with 426 jug bored out to 444 with 13:1 piston, should I be worried about the transmission failing?

Every YZ/WR owner should be worried about tranny failures. It's not a question of 'if', but 'when'. If you expect the gearbox to die, at least you wont be too disapointerd when it does.

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