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quality Temp Steve

hp gains

11 posts in this topic

Hi guys, I have a stock yz 450 2008. I was wondering if good head work and an exhaust system would produce at least 6 hp gains. How could one acheive say 60 hp on their 450. Who could you recommend for reasonably priced head work. Would I have to get an athena big bore kit and a stroker crank to acheive 60 hp. I figured someone on here may have been all through this already. Thanks guys Let us all know what hp gains you have gotten from your engine work. Steve

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The stock '08 produces roughly 51-52 hp. An exhaust will be worth no more than 1 at peak by itself under any circumstance. Head work, cams, and carb modifications are the way to go, but in the real world, it is very difficult to get 60+ out of a 450cc YZF, and extremely easy to port the head incorrectly and actually cause a loss of performance.

Big bore and stroker kits are effective, but expensive, and tend to lower the speed at which power peaks. That can be counteracted somewhat with porting to match the application.

And it is all very expensive. You could be talking about $5-6K to hit 60 hp. If you are flat tracking, road racing, or running Super Moto, you might have a reason for wanting that. If you are riding MX, or even just playing in the desert, spend your money on suspension instead, and keep the change.

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That's great advice. Thanks. Yes I sent my suspension out to be done up. Could you recommend someone that does good porting and carb mods. I would appreciate that. Steve

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Ron Hamp is one of the few people to get 60 hp out of a YZ450F. Jesse Williams has also been able to do some amazing things with five valve heads. I'm sure it isn't cheap, and it is impractical for trail or track riding.

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We acheived 62 hp with the 450 stock bore and stroke that bike base lined @ 47 hp on the same dyno it took a very special cylinder head to acheive that with + 4mm outer valves the torque was actually stronger down low than stock and the bike still made over 60 @ 11000 rpm that engine would cost around $4000 to produce again im working on a cnc head that uses stock valve sizes and has been tested and made 58 hp with good torque with the right components to go with it .

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somone posted here about a yfz head that gytr just started making.

i think it was around $2400.

then you can even sey I i ride the same engine baba crash every week. :p

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We acheived 62 hp with the 450 stock bore and stroke that bike base lined @ 47 hp on the same dyno it took a very special cylinder head to acheive that with + 4mm outer valves the torque was actually stronger down low than stock and the bike still made over 60 @ 11000 rpm that engine would cost around $4000 to produce again im working on a cnc head that uses stock valve sizes and has been tested and made 58 hp with good torque with the right components to go with it .

That is very interesting. What's your guess as far as cost for the head you're working on?

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somone posted here about a yfz head that gytr just started making.

i think it was around $2400.

then you can even sey I i ride the same engine baba crash every week. :p

Actually i dont beleive that is the head that james is using but yamaha is so secretive that who would know for sure.

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If james is or isn't, I promise you he isnt' getting 60hp on his bike (not that they can't get it....but he doesn't need/want it!)

I bet if you rode sx only, Ron would build you a head and cam combo that made 55 at peak but was tremendous off bottom....and that's probably what bubba is running.

For outdoors...then 58-60 may be reasonable...but really, I doubt he is above 55...!

Ron has done some amazing builds on the 450's, if you give him a call you may just learn something cool!

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