Can you make a 08 yz run like a 08 kx?


30 replies to this topic
  • silvy423

Posted October 20, 2010 - 09:30 AM

#21

The bike has some balls with this combo.

IMO...the Yamaha has plenty of power with just an aftermarket exhaust... more then most people can use on a track. With the stock silencer no doubt it's a dog. It makes different power than the KX (which feels more like a tractor)...the YZ motor is much smoother. I have rode a 09 YZ450 with an exhaust, some very mild head work and a HP CP piston. It motored.


So the bike will produce a nice blast of power with the head work and HC piston? That's what I want just not sure if I can get it out. Of this motor. To be honest I'm just trying to change how the bike produces it's power, I want that tractor hard hit, power RIGHT there when you need it feel.

  • grayracer513

Posted October 20, 2010 - 09:39 AM

#22

Almost all of the controlled character of the power delivery from '06 onward is the result of ignition mapping changes. If you insist on having the thrilling but not really very usable power delivery of the KXF, then what you want is either a Power Commander, a Vortex with multiple maps, or the CDI from an '03 or '04 YZ450.

  • KJ790

Posted October 20, 2010 - 10:02 AM

#23

I think you would be very surprised if you threw that KX and the YZ on a real dyno and compared them...

  • Lankyrider

Posted October 20, 2010 - 10:10 AM

#24

I have ridden both bikes and i have a yz450 2008. It's true that if you compare the two bikes stock, the KX feels faster and snappier than the YZ. As mentioned the secret is power delivery, the YZ delivers power smoothly and that's because Yamaha wanted to make the bike more user friendly. With the proper mods both bikes can be evenly fast.

  • silvy423

Posted October 20, 2010 - 11:38 AM

#25

Almost all of the controlled character of the power delivery from '06 onward is the result of ignition mapping changes. If you insist on having the thrilling but not really very usable power delivery of the KXF, then what you want is either a Power Commander, a Vortex with multiple maps, or the CDI from an '03 or '04 YZ450.


Can I use a CDI from the 03 and 04 bikes? If so should I swap out that Exh cam then? I can get a CDI for $40 on ebay worth a shot if it will work.

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  • grayracer513

Posted October 20, 2010 - 12:05 PM

#26

I am *reasonably certain* it will work. For $40, I'd try it. But I don't think I'd go to the '03-'05 exhaust cam, because you would probably loose more top end than you want to. Stick with the '06 cam instead.

If you use the early CDI with the '08 cams in place, you probably won't get what you're after that way either. The grind on all three is about the same, but the lobe centering (cam to cam) timing is different.

  • Polar_Bus

Posted October 21, 2010 - 02:05 AM

#27

I spent some laps on my buddies '06 KXF450, NO THANKS. Awesome chassis overall but way too much violent torque down low, and a killer midrange (kinda felt like the imfamous '03 YZ450F :smirk: ) . Excellent bike for any A level rider who is in TOP physicall condition to be able to hang on for 45 min... For the other 90% of us slower, in not so good physicall conditioning riders like me, i'll take the YZF's "friendly" broad power....:excuseme:

remember one fact: "Riding tired = hard dirt auger"

Edited by Polar_Bus, October 21, 2010 - 04:07 AM.


  • tl1000rlt

Posted October 21, 2010 - 02:26 AM

#28

If you can really call the bike a dog maybe there is just something wrong with it. Valves of jetting not being perfect?

  • PAdaytonaman

Posted October 21, 2010 - 04:38 AM

#29

just stop farting around. if you spent 3200 for a new bike, which is what a used bike should run you, then spend $800 or so and send the motor to PC or Tokyo mods and let them breathe some fire into it. Even if you spend up to $1500, which will get you a ripper, you still spent less than 5G's for a new bike.

just my .02

  • dvn

Posted October 21, 2010 - 06:31 AM

#30

For the other 90% of us slower, in not so good physicall conditioning riders like me, i'll take the YZF's "friendly" broad power....:smirk:

remember one fact: "Riding tired = hard dirt auger"


+1 :excuseme: I love the smooth power delivery of my 09! I doubt a harder hitting low end will really improve your lap times.

  • hoffman910

Posted October 22, 2010 - 08:33 AM

#31

I recently went from an 08 crf450 to an 09 yz450 and noticed it's lack of power terribly. Got an fmf 4.1 and rejetted it and I feel like I'm faster on the yz now. It may lack power in a few spots on every track but I feel it more than makes up for it elsewhere. Since I got the exhaust and jetted it I've been top 3 in all of my starts but 1 and have been flying. Couldn't ever get my starts dialed on the Honda with all that power. I find that I have to rev the yamaha out a bit more and I'm gonna try going up a tooth in the rear when it's time for sprockets and hopefully that will let me use 4th in more areas.





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