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Crazyzilla

YZ450F Power

17 posts in this topic

So i definatly had a chance to ride a kx450f last week. It was a 2006, it had a megabomb header and a powercore 4 silencer with some head work. I want my 450f to run JUST like that. How will the ower of the 2 bikes compare?

If i put a full exhaust system, an 08 cam, accel pump cover, will it be the same?

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Haha, I have to laugh because I know you can make the yz spank the kx. Put the exhaust on it but go with the stage 3 hotcams and have the head ported and polished while it's apart. You'll kill the kx then.

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He didn't even say IF it was a YZ. He also didn't say specifically what it is about the power delivery of the KX that he finds so desirable.

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He didn't even say IF it was a YZ.

Not specifically in the thread, but it's in the title.

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Yes, a yz450, 2006. Sorry ive never done this before im borrowing this from my friend. It just had killer low end and pulled ALL the way up top. I dont want to have rediculas power, just as much as that kx did. And by headwork, i meant cam. I dont want to port my head.

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Strong low end and a steady pull through the high end sounds like my '06. The only engine mods I have are the DRD SS exhaust and a GYT-R flywheel. If you think you want more low end than that, you should probably look into an ignition box with selectable alternate timing maps.

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What size sprockets are you using, standard? How about trying one or two more teeth on the rear?

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IM running stock gearing, i dont want to loose my top speed for desert riding. Whats the best bang for buck mods for these machines? Exhaust is a must for me for sound and performance, and the 08 cam, but what else is important? I refuse to put hotcams in my bikes. How much would say.... an x wing and acccel pump cver help?

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Stock cams ported head and a bored carb with a good exhaust will put it over 54 hp with much more over rev no loss of bottom end .Tod Dehoop rode 1 of my yzf 450s and claimed it was the fastest 450 he ever rode with usable power he pulled the factory 450s from other oems with it .

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IM running stock gearing, i dont want to loose my top speed for desert riding. Whats the best bang for buck mods for these machines? Exhaust is a must for me for sound and performance, and the 08 cam, but what else is important? I refuse to put hotcams in my bikes. How much would say.... an x wing and acccel pump cver help?

If you use the '08 cam you will lose low end power but pick up just a little on top. Put on a quality exhaust (Dr. D) and forget the other stuff.

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so basically.... pipe this thing and itll destroy that kx?
Did you read Ron Hamp's post, or just ignore it?

Forget the '08 cam. Start with a good exhaust system and see what you have. If you need more, go with the bored carb and port work (and DON'T try to port it yourself, the triple intake port is tricky).

X-wings and AP covers are wallet bait, and nothing more.

As far as gearing goes, it's a little silly to suggest the bike will have more power with lower gears. Any engine will accelerate harder in 1st gear than in 4th, but it won't go as fast, and sooner or later, you'll want to accelerate hard in a higher gear. If your bike doesn't pull hard enough in 3rd, downshift to 2nd. If there is a commonly occurring situation in which you never have the right gear available, THEN is the time to change the overall ratio, but raising the gearing may be as good a solution as lowering it.

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Alright thanks guys you really helped me out here. Wallet bait, got it. Carb work, porting, and an exhaust is the ticket. I appreciate it.

On one final note, since you guys seem to be the experts....

1. Just run all stock stuff for valvetrain right? My bike has been bulletproof with over 150+ hours think it might be time to throw in new valves.

2. Whats your take on high comp pistons...

3. Whats the BEST exhaust for this bike? Absolute best power gain EVERYWHERE?

I just might make an account on this website thank you very much fellas this is way more info then i thought id get.

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1) That's one of those questions. How's your crystal ball doing? If you wait until the valves have worn to the point where they need a shim two sizes smaller than they have now, you will know they are worn out. If you replace all the valves and have a top notch seat refinish job on the head, then you will know it's all in brand new condition. But if you do that before they wear out, youy won't know how much useful time they had left on them. My '03 was way over 300 hours without its first valve adjustment. Some race only bikes need valves at 100 hours or less. Because of the nature of coated titanium valves, it's nearly impossible to tell in advance when they might wear out. It's really anyone's guest.

2) High compression pistons are a good way to gain about 1-1.5 hp on an across the board basis, with the biggest gains at lower rpm. They can be less reliable than OEM pistons, but for the most part they work fine. If you ride in cool climates at low altitudes, you can run into trouble with fuel octane and pinging problems, but most of the time, pump premium is enough.

3) There is no best exhaust. Read this:

http://www.thumpertalk.com/forum/showthread.php?p=7489676#post7489676

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