Wrist Breaker need tips for fork set up YZ450F


9 replies to this topic
  • skymiles

Posted August 28, 2006 - 03:53 PM

#1

All right here is the deal. I have been out of riding dirt bikes for 15 years and all I ever rode was 2 strokes because basically 4 strokes were not what they are today. That behind us, I just bought a 99 YZ400F and the front forks seemed stiffer than I thought they should be so, I took them apart and found a little too much oil in them so I adjusted as per Manual and re assembled. Even with the compression and rebound as soft as it will go, it still trys to shatter my wrists on landings. What the heck, does a 4 stroke weigh so much that it needs this stiff of a fork. Any suggestions would be helpful. Thanks :thumbsup:

  • hillclimbguy

Posted August 28, 2006 - 04:02 PM

#2

Yamaha didnt make a 450 in 1999. But to answer your question, look in yamahas GYTR race book. I saw some softer springs or do a revalve to the front forks. Hope this helps.
I just bought a new 06 YZ450F and found the front forks to be real harsh. I turned the compression all the way out and still to be somewhat harsh.
My friend that has the same bike put in 06YZ250 standard springs and liked the outcome. This is for trail riding. We havent been on a track yet. We dont do much motocross.
Springs are cheaper than a revalve. Good luck

  • mxracer206

Posted August 28, 2006 - 05:13 PM

#3

All right here is the deal. I have been out of riding dirt bikes for 15 years and all I ever rode was 2 strokes because basically 4 strokes were not what they are today. That behind us, I just bought a 99 YZ400F and the front forks seemed stiffer than I thought they should be so, I took them apart and found a little too much oil in them so I adjusted as per Manual and re assembled. Even with the compression and rebound as soft as it will go, it still trys to shatter my wrists on landings. What the heck, does a 4 stroke weigh so much that it needs this stiff of a fork. Any suggestions would be helpful. Thanks :thumbsup:


The problem is probably not the weight of the YZ-400, the KYB forks Yamaha used for so long can be harsh for a few reasons. First of all they have the old rubber bottom out bumper system, it can be updated to newer material that helps. Also the mid-valve shims are probably worn causing all kinds of problems with the forks. There is a new base valve available that is a lot better than the ones you have now, I would definately make sure to use them, a huge improvemant. Your forks can be made to work well if you find the right suspension guy but would make sure he is willing to put some of the newer parts on and is going to at least replace the mid-valve shims.

  • 00YZ426FMRCD

Posted August 28, 2006 - 05:25 PM

#4

All right here is the deal. I have been out of riding dirt bikes for 15 years and all I ever rode was 2 strokes because basically 4 strokes were not what they are today. That behind us, I just bought a 99 YZ400F and the front forks seemed stiffer than I thought they should be so, I took them apart and found a little too much oil in them so I adjusted as per Manual and re assembled. Even with the compression and rebound as soft as it will go, it still trys to shatter my wrists on landings. What the heck, does a 4 stroke weigh so much that it needs this stiff of a fork. Any suggestions would be helpful. Thanks :thumbsup:


Keep in Mind that a 99 YZ400F is 8 year old technology. A lot has changed since 1999 with 4 strokes (& 2-Strokes) with their weight, motors and suspension. Next time you are at the track, see if someone will let you ride a newer 450 and see for yourself.

This isn't to say you can't get your suspension and your 400 handling smoothly, it's just going to take more effort both off and on the track. My 2000 426 had the same feel on landings. Had the suspension redone to match my weight. Key was the right springs and oil level. Night & Day diff.

  • skymiles

Posted August 28, 2006 - 06:31 PM

#5

Thanks for the advice. Are you talking about factory Yam shims and bump stops or aftermarket. If aftermarket what brand? One of the other threads I read mentioned 250 springs but I belief the guy was using it for trail riding.
That may work for that purpose but probably not for big air. What do you think?

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  • PK

Posted August 28, 2006 - 11:35 PM

#6

You should find out what springs are in your bike. Since it was obviously a used bike, the previous owner could have put in some overly stiff springs. The stock springs were pretty soft and most folks who MX'd installed stiffer springs. Bottom line is that something isn't as it should be. Either worn internal fork components, stiff valving and/or stiff springs are most likely the culprit. How big was the previous owner?

I would gather up some $$ and buy the right springs and if you don't know how to disassemble a set of forks, take it to a reputable suspension shop, not the local dealer, and have them go through them. Race Tech makes valving systems and alot of folks recommend removing the midvalve since the bike blows right through it anyway.

One other question: is the bike bottoming out and that's what makes it hurt your wrists or is it so stiff it doesn't bottom and that hurts your wrists?

  • mxracer206

Posted August 29, 2006 - 04:20 AM

#7

Thanks for the advice. Are you talking about factory Yam shims and bump stops or aftermarket. If aftermarket what brand? One of the other threads I read mentioned 250 springs but I belief the guy was using it for trail riding.
That may work for that purpose but probably not for big air. What do you think?


It does not matter what size bike the springs are for as long as they are correct for your weight. The reason I spoke in detail about the internals is because if the mid-valve shims are bent no matter what alse you do the forks will be terrible. The only thing available from Yamaha is the new bumper, in 2001 they use the new material. Race Tech has all of the stuff I mentioned but depending on what suspension shop you choose they may use something else. You will have to spend some money to get the forks better.

  • skymiles

Posted August 30, 2006 - 03:33 PM

#8

Thanks for your help. To answer your question the previous owner was not any larger than myself, around the 170 -180lbs. But he didn't have time to ride it much or seem like he had the knowledge how it should feel. As far as bottoming out I don't think thats whats happening, it's more like the bone jarring shock comes at the beginning of compression stroke, at first contact of the front wheel with the ground. But the rest of the compression stroke is smooth. And I know what your probably thinking, I wondered myself if maybe one of the forks was bent but thats not it.

  • PK

Posted August 30, 2006 - 09:13 PM

#9

It's pretty hard to bend a fork, I think MXracer has some great advice as well. All of the topics that have been brought up would be addressed by a fork rebuild by a good shop.

  • tammie

Posted September 06, 2006 - 05:44 AM

#10

i have a 99 yz400 and swamed out the front stock fork springs for softer "racetech" fork springs suspension is great, im only 140lbs though........also i swamed the rear spring for a WR rear spring.....ive had no suspension problems with this set up.........





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