[jethro450]

hey guys, I've rebuilt, revalved, redone forks hundreds of times. This last time I thought I did everything right but apparently not.

On my 08 450r when I pull a wheelie, jump, or anytime my front end comes off the ground... The fork seems to rebound or fully extend too quick. It feels like 90% of the extension stroke rebounds correctly, but the last 10% it just slams out to the end. It's not a pure metal on metal clank, but it's enough that it's noticeable.

Not enough oil in the inner chamber? I feel my clickers are fine cause normal riding/racing it feels good. It's just that last little bit of stroke that is worrying me.

[JimDirt]

A few questions

What is your weight and current spring rate and riding ability (A,B,C, ETC , young guy , older like me , in mid 50's) ??

Are you riding Moto or Off-Road/Enduro's , or both ??

do you have free Sag ?? , fork and shock ?? , if so how much (fork/shock)

Are you meaning not enough oil in the OUTER chamber ?? , as the inner chamber should be full unless you did not bleed it properly , otherwise you will have air in the closed cartridge and that will make all sorts of tuning issues present

When you re-valved , did you change the Rebound stack or just the Compression stack ?? , if so , what changes did you make ??

Did you notice any wear on the bushings for the Rebound , if so did you replace them ?? (worn bushings can cause clanking when the fork tube is fully extended)

Did you mess with the Mid Valve ??

A Wheelie , should not do anything significant to the travel or rebound , its just not enough force to make a noticeable impact on a clicker setting unless you slam on the rear brake and slam the front end down , unless something else is off/wrong

If your flat landing or landing off the throttle , then its not going to make much difference how you valve or spring it , the bike will bounce a bit , as its absorbing the entire impact , so its going to react differently than if you landed on a ramp/jump face , or even nose high or down or on the throttle , so have you ruled out technique as a possible factor ??

Have you tried turning the Rebound all the way in , and all the way out to see if it makes any (better/worse) difference over the same area (same area meaning the same obstacle that you noticed the issue on) ??

When testing , are you doing the same thing at the same place (like the same jump , etc,etc) ?? , since its about impossible to set up suspension for EVERY obstacle or every part of a track you encounter , what setting or valving works better some areas , might make it worse in others , its all a compromise to set it to work well or OK in all areas , or set it for one area , and just hold on for the ride on the rest (basically)


Basically the symptoms your describing are from the Rebound being too FAST , if your clicker settings are not affecting the speed enough , then i would say the issue is in the stack itself (dirt , debris holding the shims open , etc) , if you changed the rebound stack configuration then this would be the cause , and you need to look over the stack to determine if you used the wrong shim , or amount of shims

If the stack is too loose then it will not work properly , you need to fill up the space made from swapping out or removing shims , if oil is going thru the stack easily , it will be like its opened up , and it will hit hard , also , the compression setting will affect rebound somewhat , as they work together even though they are separate , so if your way to the end of the clickers on your Compression clicker , then it could be the Compression stack is not working as it should and the rebound stack is trying to make up for it

I am assuming you did your shock as well , if so , did you change the rebound on it ?? , if so how does the rear of the bike act , does it kick to the side off jumps ?? , does it swap in whoops ?? , does it kick up on braking bumps ?? , does it accelerate well in rough conditions ??

OK it was more than a "few" questions

[jethro450]

Holy crap JimDirt! Well I've got a few answers for ya. Maybe I'll answer within your quoted text.... See below.....

A few questions

What is your weight and current spring rate and riding ability (A,B,C, ETC , young guy , older like me , in mid 50's) ??
......Weight, you getting personal huh? Ha ha. 175. Expert. I even have 1st place trophies from the expert class. So I'm not slow. 36 yrs old......

Are you riding Moto or Off-Road/Enduro's , or both ??

.....Everything. Valved for expert off-road. It's basically slightly more plush than stock MX. I actually don't think any of these questions have anything to do with the problem as I've ridden with the same re-Valved suspension since 2009. The issue just started after I replaced all the oil a couple months ago..... And honestly, I doubt someone with less experience would even notice the problem as it still rides awesome. But since I and my machine are ONE, I notice. Ha ha

do you have free Sag ?? , fork and shock ?? , if so how much (fork/shock)

Are you meaning not enough oil in the OUTER chamber ??.... No.... , as the inner chamber should be full unless you did not bleed it properly ,

.... This is what I think the issue is. I'm thinking I didn't get the inner bled correctly but I was wondering if that would cause the issue I explained. .....
otherwise you will have air in the closed cartridge and that will make all sorts of tuning issues present

When you re-valved , did you change the Rebound stack or just the Compression stack ?? , if so , what changes did you make ??
.......Both changed, both done years ago.

Did you notice any wear on the bushings for the Rebound , if so did you replace them ?? (worn bushings can cause clanking when the fork tube is fully extended).
......Nope, they looked great.

Did you mess with the Mid Valve ??
....... Yup, years ago. Again, the only change recently was oil.

A Wheelie , should not do anything significant to the travel or rebound , its just not enough force to make a noticeable impact on a clicker setting unless you slam on the rear brake and slam the front end down , unless something else is off/wrong.

.....no issues with compression, but when I pull the wheelie, I feel the front end fully extend....

If your flat landing or landing off the throttle , then its not going to make much difference how you valve or spring it , the bike will bounce a bit , as its absorbing the entire impact , so its going to react differently than if you landed on a ramp/jump face , or even nose high or down or on the throttle , so have you ruled out technique as a possible factor ??
.....Yup, ruled out.

Have you tried turning the Rebound all the way in , and all the way out to see if it makes any (better/worse) difference over the same area (same area meaning the same obstacle that you noticed the issue on) ??
.... I may try this before pulling the forks off again, easy thing to check. Having said that, it rides trails and desert at speed perfectly. Turning it all the way in or out would mess it up. ....

When testing , are you doing the same thing at the same place (like the same jump , etc,etc) ?? , since its about impossible to set up suspension for EVERY obstacle or every part of a track you encounter , what setting or valving works better some areas , might make it worse in others , its all a compromise to set it to work well or OK in all areas , or set it for one area , and just hold on for the ride on the rest (basically)
...... It does the same thing anytime it fully extends, doesn't matter the object that causes the extension.

Basically the symptoms your describing are from the Rebound being too FAST , if your clicker settings are not affecting the speed enough , then i would say the issue is in the stack itself (dirt , debris holding the shims open , etc) , if you changed the rebound stack configuration then this would be the cause , and you need to look over the stack to determine if you used the wrong shim , or amount of shims

..... Having just had the whole thing apart for an oil change only, I do wonder if the stack got loose somehow. That's a good thing to check......

If the stack is too loose then it will not work properly , you need to fill up the space made from swapping out or removing shims , if oil is going thru the stack easily , it will be like its opened up , and it will hit hard , also , the compression setting will affect rebound somewhat , as they work together even though they are separate , so if your way to the end of the clickers on your Compression clicker , then it could be the Compression stack is not working as it should and the rebound stack is trying to make up for it

I am assuming you did your shock as well , if so , did you change the rebound on it ?? , if so how does the rear of the bike act , does it kick to the side off jumps ?? , does it swap in whoops ?? , does it kick up on braking bumps ?? , does it accelerate well in rough conditions ??
....she rides perfect. I'm just picky and feel the minor difference....

OK it was more than a "few" questions

[JimDirt]

LOL , sorry , but you did not specify any of the things i mentioned in your post , so just trying to be thorough , as you did not mention that you only changed oil , since your post said "I've rebuilt, revalved, redone forks hundreds of times. This last time I thought I did everything right but apparently not." which to me means you re-valved them this time ... my bad ...

Now that we have that out of the way ......

Yes not bleeding the inner chamber correctly can cause what your experiencing , since #1 , you will have oil cavitation , because of the air disrupting oil flow , and causing air pockets , just like in a boat , when the prop cavitates because its coming out of the water , you loose forward momentum

In the closed chamber , your allowing air to disrupt the flow of fluid and you get the exact same effect , the valving cant open when it needs to in the compression stack , AND , your sucking/pushing air into the Rebound valving as well so the flow does not have the pressure behind it to push open the valving WHEN it should in the stroke , the oil works under pressure to open the valving , because of the air and the lower oil level , then it will throw both compression and rebound off enough to give you all sorts of issues , kind of like your describing

#2 , with low oil , you wont have the volume of oil needed to push the valving open , and and it will affect your Free Sag , because the pressure is allowing the forks to sag because of the lack of pressure holding the Rebound Rod out , your main springs only hold the bike UP in the stroke , it has some effect on Free Sag , but not all of it , the valving and oil in the inner chamber does everything else , the oil in the outer chamber is mainly for lubrication , and bottoming resistance

So recheck your bleeding procedure and see if you notice a difference , measure the oil you remove from the cartridge and make sure it was enough


Oh , and either way , your getting a long post from me , its just the way it works with me

And for future reference , if you type within the quote , just either change the font color , or , highlight what you typed and hit the big B (the first one at the top) for BOLD , that way i dont have to search the entire text for your reply

[jethro450]

Thank you JimDirt for your time in replying and confirming my suspicions. I'll tear it down when I get some time and rebleed that inner chamber. I may even replace all sliders and bushings just for the heck of it.

[JimDirt]

No problem , hopefully that solves your issue

Also , make sure when your putting the Rebound nut on that you have it tightened down like it should be , if you don't get it on enough threads on one fork , then that fork will extend farther than the other side and can also cause the clanking noise since the shorter side will top out before the other side

you can confirm the correct height on the rod by the manual specs , as well as the clickers themselves , if you can click one Rebound adjuster to 26 clicks , and the other to 24 , then it means that the 24 side is shorter than the 26 , so it will top out first , this can be noticed right down to 1/2 a click , and can also be confirmed by measuring from the fork lug to the fork seal , it should be EXACTLY the same measurement on both forks , so make sure they are both the same , the same way you make sure your fork lugs are equal height when installing the forks in the clamps to avoid fork bind and allowing your axle to slide in and out with no effort , its the same with the Rebound nut !!