forks revalved... feels like a sportster


17 replies to this topic
  • elsinoredaze

Posted January 03, 2007 - 08:22 PM

#1

05 450 forks were leaking and I decided to have them revalved.I'm 250 lbs and here is how they came back.

.50 springs (replaced .48's)
225 ml maxima oil/ 2.5 weight
rear sag set at tuners recommended 100 mm
tuned for MX

bike is beating me to death.Arm pump like I've never experienced.Feel like I've got to stand on the front to exit turns without washingI've moved the compression to 15 clicks out and that helped a great deal but 15 clicks is way more than I've ever run.Any help/tips will be appreciated.

  • 642MX

Posted January 03, 2007 - 08:32 PM

#2

Who revalved them? Most tuners will do it over for no charge if your not satisfied.

  • dwnlowx

Posted January 04, 2007 - 02:54 AM

#3

i noticed since my revalve that the bike is very uncomfortable while sitting down but very plush when standing

  • matts06yzf

Posted January 04, 2007 - 08:44 AM

#4

05 450 forks were leaking and I decided to have them revalved.I'm 250 lbs and here is how they came back.

.50 springs (replaced .48's)
225 ml maxima oil/ 2.5 weight
rear sag set at tuners recommended 100 mm
tuned for MX

bike is beating me to death.Arm pump like I've never experienced.Feel like I've got to stand on the front to exit turns without washingI've moved the compression to 15 clicks out and that helped a great deal but 15 clicks is way more than I've ever run.Any help/tips will be appreciated.


yeah who did the revalve?

  • Wyatt

Posted January 04, 2007 - 09:12 AM

#5

Like stated above, take it back to your tuner. If he is a good suspension guy, he will listen to your complaints and make the necessary adjustments.

  • elsinoredaze

Posted January 04, 2007 - 11:06 AM

#6

I don't want to put the shop name out but it is a nationally respected suspension shop.I'm just trying to get some ideas about what might be going on before I call em...

Thanks

  • Wyatt

Posted January 04, 2007 - 11:49 AM

#7

Just call them and explain exactly what you are feeling when riding. They will take your input and make a decision on what needs to be changed. You know what it is doing better than anyone. They should be able to help you.

  • kawirider

Posted January 04, 2007 - 03:04 PM

#8

i noticed since my revalve that the bike is very uncomfortable while sitting down but very plush when standing


Same here. (for the most part) I had my suspension revalved by a local shop. At first I thought he hadnt done a very good jobe. Why? Because when I would sit in the middle of the seat and try to take it easy, it would beat me up. However, when I really got my balls on the gas cap where they are supposed to it grabbed everywhere. Sitting down still isnt comfortable (which is true for any mx bike w/a stock seat) but now standing up is very smooth and controlled.

  • StPeters21

Posted January 08, 2007 - 07:29 PM

#9

also you prob need a stiffer rear spring to even things out. right now your front is trying to handle all the weight.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Baron Von Beard

Posted January 08, 2007 - 10:48 PM

#10

It sounds like the shock spring is too soft. When you sit and put more weight on the rear, if the suspension isn't balanced it can take too much weight off the front end which can cause it to feel finicky and harsh, that's why it's better when you are standing. Tell your suspension guy exactly what you told us and they should be able to fix it no problem. Just remember, no one benefits from embellished abilities and/or underestimating your weight, when it comes to suspension tuning. Also make sure that you are in fact setting the sag correctly, it's definitely a two man job. I know how some guys can get with trying t do it themselves, or heaven forbid, have their wives help them! :lol:

  • jroon

Posted January 12, 2007 - 07:50 PM

#11

Hello Folks, just bought a 2001 YZ 426 today, plan to use it on the ice and maybe some Vet motocross. You mentioned sag in this thread, last time I set it was on my 1985 490 and it was about 100mm or 4 inches with me on the bike. Does this hold true for the modern bikes?

  • RAMARION

Posted January 13, 2007 - 05:37 PM

#12

Hello Folks, just bought a 2001 YZ 426 today, plan to use it on the ice and maybe some Vet motocross. You mentioned sag in this thread, last time I set it was on my 1985 490 and it was about 100mm or 4 inches with me on the bike. Does this hold true for the modern bikes?



yes, still the same

  • RAMARION

Posted January 13, 2007 - 05:45 PM

#13

05 450 forks were leaking and I decided to have them revalved.I'm 250 lbs and here is how they came back.

.50 springs (replaced .48's)
225 ml maxima oil/ 2.5 weight
rear sag set at tuners recommended 100 mm
tuned for MX

bike is beating me to death.Arm pump like I've never experienced.Feel like I've got to stand on the front to exit turns without washingI've moved the compression to 15 clicks out and that helped a great deal but 15 clicks is way more than I've ever run.Any help/tips will be appreciated.


if 15 clicks helped......you might be a few more clicks away to perfect. Take a full day of practice and use exclusivly for susp testing.

Run a few laps with the setting set at max, min, and netrual. Do this on forks and shocks, compression and rebound.

This will teach you how suspenison reacts. After this session is complete, you'll know more than 95% of ALL RIDERs (that average is probally closer to 99%:lol: )

good luck.

btw, been there, done that and I learned by using the method as I stated.

You don't think the Pro's are asking what the other racers are using???? You must learn for yourself.

  • vettechic

Posted January 14, 2007 - 01:26 PM

#14

the problem is with the rear spring. way too soft. when you load the suspension it will cause the tail to set too low, causing the front to go long changing the dynamic trail too much, when you load the front more you dynamicaly reduce the trail causing the bike to turn better. by adding more spring to the rear it will hold the rear up and keep the geometry correct. also a heaver spring with less preload will be "softer" than a light spring with more preload. when you reduced the comp in the front this allowed the front to set lower in the turn, basicaly a band aid for the problem. also if you open the comp too much the forks will blow through the stroke hitting the bottom and giving you a harse ride. when you stand on the pegs you are changing the center of gravity, once again a good band aid. remember extra trail will make the bike harder to steer and hold down in the turn. get your shock revalved and resprung for you weight, add the comp back to the front and the bike will be much better.

  • grayracer513

Posted January 14, 2007 - 07:54 PM

#15

... a heaver spring with less preload will be "softer" than a light spring with more preload.

extra trail will make the bike harder to steer and hold down in the turn.


A heavier spring will be heavier, regardless. A rate of say, 5.5kg/mm means it will take 55 kg to compress the spring 10mm, and an additional 55 kg to compress it another 10mm. This rate remains constant throughout the range, from a free spring to coil bound. What happens is that a spring that is too soft requires an excessive amount of preload to get the race, or rider sag set right, and that results in too little free sag, (using race sag to determine spring rate) which makes the rebound damping difficult to set up. Also, since the spring is too soft, the compression damping has to be set higher to compensate, and the bike feels harsh.

The second statement above is at odds with the fact that decreased offset clamps, which are used to make bikes turn in more easily at lower speeds, increase trail.

  • racer569

Posted January 15, 2007 - 06:44 AM

#16

grayracer513, what is happening is "dynamic" geometry, not "real" geometry. real geometry is the bike measured on the hang, nothing has an effect except the true geometry ie clamp offset, ride height, tire sizes... dynamic geometry is what happens os you enter the turn, g-force, spring rate, preload, standing, setting, how much you ate for dinner.... changing the offset at this point may or may not help the situation, but the main problem still remains, "dynamicly" the bike has too much trail, the rear is setting too low and it wants to run wide. thus when you "stand" on the front it gets better.

we would all love to believe the springs are constant through their full range of movement, but they are not. all springs will increase their rates as they reach coil bind. grab a few springs and run them to bind and you will see what i mean, over the years thy have gotten better but.... the statement of a "heaver" spring rate feels "softer" was in response of moving from a .48kg/mm spring to a .50 kgmm spring, once you have set the proper sag the .50kg/mm spring will have less preload thus less rise as it goes through the stoke. the statement that a softer spring will require too much preload to get the proper sag, totaly correct, i think that was the point all along. the statement "that i am running my compression at 15 clicks out, and i have never run it that far out before" should also make you think what if the fork is "blowing" through the stroke, maybe it's going to the bottom, maybe it is getting to coil bind..... all of these thing can make the bike feel harsh.

remember the rider said when i stand up it gets better???? he changed the dynamic geometry of the bike not the real geometry of the bike. most riders know and can say what the problems are, you just have the listen to what they say.

  • grayracer513

Posted January 15, 2007 - 09:37 AM

#17

Given that the OP stated his front springs were changed, but his rear is the lower rate OEM part, any centrally distributed increase in load will compress the rear farther and sooner (ignoring damping) than the front, causing the bike to rock (pitch) rearward as the suspension compresses. The factor that gets changed the most under those circumstances, as far as steering geometry is concerned is steering head angle. Trail, of course, does increase, but very slightly, relative to the shift in head angle. An increase in head angle will make the steering less responsive and tend to push. Increasing trail tends to make the steering feel lighter and easier to turn in as the bike is leaned over, and increasing trail is, as I said, what most[/I offset triple clamps are about. Your statement that increasing trail made the bike hard to steer is the only thing I found fault with. Too much may affect the quality of the steering negatively, but it won't make it harder in tight corners.

Springs respond only to increases or decreases in the load placed on them, and the only dynamic element they would know about is the weight increase attributable to the G force of an impact and the resulting multiplication of the load they carry. Coil springs have no ability to do any damping, and except for their internal inertia, do not respond to changes in compression or extension speed. The rate of single rate springs does remain very constant through the entire range, as I said. There is a very minor and short-lived rise in the first 2mm sometimes, and [I]at the point of coil bind
as well. What happens there is that the coils do not bind uniformly, but begin to bottom against one another randomly within the spring. Each coil that binds increases the spring rate by effectively shortening the spring. But this whole process takes place only within the last 2-5mm of compression, and is moot in any case, since modern MX springs don't coil bind when made right. Within the working range of the spring the rate will remain constant within a single digit percentage.

A 100 lb/in spring with 125 pounds placed on it will require a 1/4" of preload to compress an inch. If the rider adds another 100 pounds, it will compress another inch. When this combination takes an impact of 1g, the load increases by 225 pounds, and the spring is compressed 2 1/4 inches farther.

A 75 lb/in spring with the same loads placed on it needs to be preloaded a full inch to support the combined bike and rider weight given above at the same 2 inch compression, and will only sag .65 inches under the 125 poiund weight of the bike. When the same 1g impact is applied, the spring will compress 3 inches farther (225/75). The rate of the softer spring compressed farther on preload does not rise more per inch of travel than the heavier spring does. But if we say that the compression under the one G load should be limited to 2.25" in both cases, then we have to increase the damping with the softer spring.

The biggest problem with the OP's setup is that the rates are mismatched front to rear, setting up the dynamic problem you were alluding to. The observation that the suspension works better when standing is not uncommon even on properly set up bikes, and is sometimes simply an indication that the rider sits too far back. It's different in this cases, of course. But if both ends were too soft, the problem would primarily be one of excessive harshness due to the extra damping required to prevent bottoming.

  • racer569

Posted January 15, 2007 - 10:18 AM

#18

wow, good job, could not have said it better.





Related Content

Forums
Photo

James Stewart back on a YZ450F by YamaLink


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F


Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies
Forums
Photo

Michigan Motocross Tires by 288yz450


Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply
Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.