2007 yz450f How to get the "spin" out


11 replies to this topic
  • scottwvu

Posted August 17, 2010 - 01:51 PM

#1

GREETINGS! I have a question for all you yz pros! I recently purchased a 2007 yz450f. The past two bikes I have owned were 2004 CRF450's. I love the bike, but it seems as if the back wheel is too quick to break free in the top-end, almost like a two-stroke.
I happen to work at a Yamaha dealership, so I asked one of our techs, and he said going up in the rear (meaning gearing DOWN) would only make it worse. Tires are fine. Any ideas or suggestions?
Also, the engine makes a funny noise when the clutch lever is out, but sounds completely normal while holding the lever in. My tech said this is normal. Any help would be GREATLY appreciated! THANK YOU!

  • grayracer513

Posted August 17, 2010 - 02:36 PM

#2

Regarding the noise, if it's a growling sort of rattle, it's normal:

http://www.thumperta...282#post5362282

The YZ450 has very little rotating mass in the engine, and a flywheel smaller than its gas cap. So, yes, they are a bit snappy. I'm a little surprised that you don't think the CRF was worse, but either way. Gearing it higher Larger front/smaller rear) will help a little, but won't really make that much difference in the lower gears. I think you'll find the best improvement will come from using a heavier flywheel. I use the GYT-R "Off-road" unit (GYT-2S297-50-50), and I find it helps quite a bit.

  • idahoexcr500

Posted August 18, 2010 - 06:43 AM

#3

I also have an 07YZ450F. I used to have an 05 CRF450R and think the Yamaha hooks up so much better, no comparison. I am running MX51 tires front and rear. They made a big difference. The rear really hooks up, I am running stock gearing as I play ride and like the top end speed, for MX I would go up a tooth or two in the back. I think the Yamaha is much more mellow than the Honda off the bottom but it revs out much better. A FWW would help for sure. Get the suspension dialed in for your weight, maybe that will help. As Gray said, the noise is normal, mine does it too.

  • Wiz636

Posted August 18, 2010 - 07:45 AM

#4

Are you certain that it is the rear wheel breaking loose and not the clutch slipping under high HP?

  • scottwvu

Posted August 18, 2010 - 04:30 PM

#5

Are you certain that it is the rear wheel breaking loose and not the clutch slipping under high HP?


I never really considered this. I don't THINK that is what it is. I have only ridden it twice. Once in our dealership parking lot and for an hour in the woods. I know popping "power wheelies" (throttle only) is difficult on asphalt due to the wheel spin, and if I remember correctly, the rear will start to slide out from under me in the woods (when the spinning is happening).

The CRF's I had all had more bottom end and seemed to spin LESS than the yz. I will look into the flywheel weight!

  • mikedabike

Posted August 18, 2010 - 05:30 PM

#6

I never really considered this. I don't THINK that is what it is. I have only ridden it twice. Once in our dealership parking lot and for an hour in the woods. I know popping "power wheelies" (throttle only) is difficult on asphalt due to the wheel spin, and if I remember correctly, the rear will start to slide out from under me in the woods (when the spinning is happening).

The CRF's I had all had more bottom end and seemed to spin LESS than the yz. I will look into the flywheel weight!


You must be whackin the throttle. My 07 probably has the least off idle wheelspin of any bike I have owned. What gearing are you running and what air pressure in the tires. Also is the throttle stock or does it have one of those quarter turn jobs?

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  • scottwvu

Posted August 19, 2010 - 07:01 AM

#7

It's not off idle. It's at the very top of the powerband. Stock throttle (for now, getting an aluminum throttle). Stock gearing, although I plan on going to a 51 rear.
I had a 2005 yz250 2-stroke that would break the rear-end free in the upper revs. The 450 isn't as bad, but worse than the CRF's I had.

  • mikedabike

Posted August 19, 2010 - 06:16 PM

#8

It's not off idle. It's at the very top of the powerband. Stock throttle (for now, getting an aluminum throttle). Stock gearing, although I plan on going to a 51 rear.
I had a 2005 yz250 2-stroke that would break the rear-end free in the upper revs. The 450 isn't as bad, but worse than the CRF's I had.


I am sure the flywheel would help. Sure you just don't need some practice with throttle control? One of my favorite things about my 07 is that the throttle seems very linear. The lower gearing is probably not going to help.

  • WB450

Posted August 20, 2010 - 10:26 AM

#9

Regarding the noise, if it's a growling sort of rattle, it's normal:

http://www.thumperta...282#post5362282

The YZ450 has very little rotating mass in the engine, and a flywheel smaller than its gas cap. So, yes, they are a bit snappy. I'm a little surprised that you don't think the CRF was worse, but either way. Gearing it higher Larger front/smaller rear) will help a little, but won't really make that much difference in the lower gears. I think you'll find the best improvement will come from using a heavier flywheel. I use the GYT-R "Off-road" unit (GYT-2S297-50-50), and I find it helps quite a bit.


It helped my 07 a lot.:bonk:

  • scottwvu

Posted August 22, 2010 - 06:28 AM

#10

I am sure the flywheel would help. Sure you just don't need some practice with throttle control? One of my favorite things about my 07 is that the throttle seems very linear. The lower gearing is probably not going to help.


I went off-road riding this weekend. Through some really crappy almost swamp-like trails that had TONS of roots, rocks, ect. in the bottoms, hillclimbs and fast fire roads on top. I have to say that this is the best 450 I have ever ridden.

Sure, I think throttle control was a BIG part of it. I just hadn't spent any time on it. I frankly rode my a$$ of yesterday and love pretty much every aspect of this bike. Thank you all for your answers!

  • Polar_Bus

Posted August 24, 2010 - 04:02 AM

#11

It's not off idle. It's at the very top of the powerband. .


With this said, now I am also thinking it's time for a new clutch. Can you take the bike somewhere safely down a paved road ? Shift the bike quickly up into like 4th and pin the throttle WO, if your rpm's come up much more quickly than your speed you have a slipping clutch.

  • scottwvu

Posted August 24, 2010 - 02:08 PM

#12

I'll try this. Thanks!





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