Fork oil height.

[TD3]

On USD KX forks do you measure the oil level with the inner rod assembly up or down?

Why am I asking? ..Well.....I took the bike out this morning to try and nail down the jetting and also play around with the suspension. The jetting is continuing to be PITA so I figured I'd try to dial in the suspension for faster riding. The bike seems to bottom harshly. So much so, that it got away from me on a sharp root and down I went. I now have a little less skin on my left forearm and a tender ankle, but I'll live

I took the forks off and decided to make my first attempt at a quickie oil change and adjust the oil level. I know... I know.... I should take them completely apart, but that just isn't going too happen this time. (Jason will get the complete rebuild)

So any helpful hints for a rookie?

[KDXGarage]

Measure it with the springs out and the outer tube all the way down. Be sure to pull the damper rod completely through its travel several times to bleed air from the cartridge, plus be sure to keep the oil above the holes and all that.

Getting rid of SOME gunk and wore out oil is better than NONE.

One skinned forearm + one tender ankle = one story to tell at work

[Indawoods]

Sounds like you need to adjust your compression clickers.

What is your oil level now? I put my oil in with the rod in the down position as I think this is correct.

[TD3]

Hey Guys thanks for the promt replies!

One skinned forearm + one tender ankle = one story to tell at work

I forgot to mention my now "used" FMF pipe. That thing only lasted 3 weeks with no dents!

Jason: If I measure it with the rod down then it looks like the bleed holes between the tubes are exposed. Does that make sense? Do I just fill it up, pump/bleed then let the rod down and adjust the level?

Sounds like you need to adjust your compression clickers.

Indawoods: I was under the impression that the compression setting where more for low speed compression. I know that when I first put the forks on it was fairly harsh over the choppy slow stuff, so I backed out on the clickers. I'm not sure what springs are in the forks, but they do feel a little soft. I'm just trying to get through this season before doing a complete rebuild front and rear.

My wife suggested I slow down Sometimes I just can't figure out where her heads at

[Indawoods]

For a temporary halfassed fix try to use 10wt fork oil at around 100mm. This might get you through the season til you can reshim and respring 'em.

[TD3]

Inda:

I'm all over that "halfassed" fix cept, I'm using Mobile 1 ATF!

Seriously though, even in their present state the KX forks are still better than the original forks that were on the bike. It rides pretty good at a moderate pace, but they don't like to be pushed ......yet.

Thanks again for the response!

[KDXGarage]

You have to fill it over the bleed holes in the inner tube, then remove the oil.

Stock oil level is 100mm, with the highest level in the adjustable range at 70mm.

Stock compression adjustment is 8 clicks out.

If you are just bottoming out too much, then try to raise the oil level for now.

Watch the oil weight, as all those roots may "buss you up a good un" if you get it too harsh.

Start another thread on the jetting, so we can confuse yu twice instead of just once.

[Indawoods]

Do you suggest he cut the difference between stock height and the highest level then? Say 80mm to 85?

ATF is not fork oil and I know alot of guys use it... even the pro tuners but viscosity is not consistant since it is not a required element of ATF.
For that reason, I won't be using it. I think generally it is between 5WT and 7WT but can vary from bottle to bottle.

[TD3]

Well it's all back together.

I went with 95mm oil height. I didn't check the old oil height, but it was lower than where I ended up. I'm going to give it a test ride tomorrow.

Thanks again for the help.

[KDXGarage]

Cool. With the ATF, it should be heavier than even fresh 5 weight fork oil, so with the oil a little higher, you should be able to tell a difference.

I don't know if you got it, but I sent you an e-mail on it all.

[skipro3]

From the Factory Service Manual for 1999-2002 KX125 and KX250:

KX125: 108~112mm (L1/L2 Models)
88 ~ 92mm (L3/L4 Models)

KX250: 108~112mm
86 ~ 90mm (L2 Model)
68 ~ 72mm (L3 Model)
73 ~ 77mm (L4 Model)

Adjustable Range KX125/250: 102~145mm
60 ~120mm (L2~L4 Models)

Note:
L1=1999
L2=2000
L3=2001
L4=2002

FWIW: I set my 2002 KX250 forks to 98mm using 5wt Belray oil.

[KDXGarage]

Thanks for the info, skipro3!

[canyncarvr]

RE: LSC/HSC

By definition (mine ! ;) ) a 'sharp' root would cause a lot of fork movement is a short period of time. That is 'HighSpeedCompression' by correct definition. That will be most effected by spring rate, oil viscosity and air shock (oil level).

Still, the clickers allow more or less oil to pass depending on the setting. While they can't handle HighSpeedCompression demands, they do still flow some oil. Costs nothing to back them out and see if the ride improves, click'em back in if it doesn't.



I don't understand 'bottom harshly'. When the suspension hits its bottom and jars to a stop, it's harsh? Or it bottoms too early/easy/soon?



Looks like you have a KX manual, ski!! I'll bet Jason will buy you a beer when he gets out here for a ride if you send him some xoxed copies of the fork/shock sections!

[TD3]

A quick follow up.

I took the bike out in the rain yesterday so I wasn't able to push things too hard. It definitely has a firmer ride throughout the stroke (at least what I used).

I also may have found a discrepancy in the article at the top of this page for the KYB rebuild. The picture titled fig.2 shows the "short rebound adjuster rod" going in backwards. BikeBandit shows the rod the other way and I have found references of this mistake on other forums using Google search. Any thoughts?

I don't understand 'bottom harshly'. When the suspension hits its bottom and jars to a stop, it's harsh? Or it bottoms too early/easy/soon?

Good question. When riding at a moderate or slow pace the forks are very comfortable. They soak up the bumps fine and track very well. When I'm really on the gas and attacking the terrain the forks become unpredictable and when they get to the end of the stroke they are harsh, including bottoming out. Being of French/Canadian decent it's somewhat difficult to explain without using my hands!

[KDXGarage]

Put a little more Earl in there if they are still bottoming out, TD3.

Mais oui!


I saw what you are saying on the Doug Jenks article. I will sift through many diagrams later to check for proper orientation.

[canyncarvr]

To shine a beacon on my own ignorance...

I didn't get any more'n one such rod(s) out of my fork(s). Oh well...I didn't let it keep me awake nights.......ZZZzzzZZZZzzz

snort...oh...uh...where were we?? oh...

re: 'attacking...unpredictable...'

I could imagine that is what you could expect from an un-damped bike.

re: bottoming

OK if it happens very seldom in your normal riding routine. Otherwise, as Jason said, more oil...or more spring.

[KDXGarage]

cc, since you have the seat height shortening links, do you think that may be cause for you to enjoy the "only" 3mm of preload so much? I wonder if the front of your bike was sitting up a bit high after the links were installed. This is KDX fork related and now KX fork related, too. If so, it makes me wonder if 3mm would put the front end angle a bit low for the other 99% of people out there without lowering links.

[canyncarvr]

I'm sure it makes a difference. Geometry tends to do that (make differences).

My forks went from uncompliant to compliant with the preload change..backwards from what I would suppose a lowered rear to do.

I dunno.

I didn't change back to the OEM pullrods in an attempt to effect the fork action.

Probably would, though.

Good point!

!!WARNING!!

Mine are bigger'n yours!!

Well...probably. Likely longer anyway!

[KDXGarage]

Do you mean the pull rods are longer??

[canyncarvr]

That is a true statement. 1.5mm longer as a matter of fact.

Hey...they're BOTH longer!! That's !