Stock H series forks - more rebound?

Got questions? We got answers....
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Stock H series forks - more rebound?

Post by gregp »

I am very happy with the stock forks on my '04 KDX, but I would like to get a bit more rebound damping - without going to heavier oil (subsequently affecting the compression damping). There is a small hole at the top of the damper rod, which appeared to be the only orifice that regulates the rebound damping. Can anybody educate me on any other sytem components or ports that might affect the rebound damping characteristics of these forks?
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
User avatar
David_L6
Gold Member
Gold Member
Posts: 235
Joined: 01:07 am Jun 04 2010
Country:
Location: Northwest Louisiana

Re: Stock H series forks - more rebound?

Post by David_L6 »

>|<>QBB<
gregp wrote: I would like to get a bit more rebound damping - without going to heavier oil (subsequently affecting the compression damping).
I believe that is why a lot of people install forks off of other motorcycles....
2000 KDX200 / 2002 CR250 / 2003 CR250 / 2008 TT-R230 / 2011 Brute Force 750 / 2012 Brute Force 750 EPS
User avatar
Julien D
KDXRider.net
KDXRider.net
Posts: 5858
Joined: 07:53 pm Nov 07 2008
Country: USA
Contact:

Post by Julien D »

I am very happy with the stock forks on my '04 KDX
Now there's something you don't hear very often!

Not much you can do. The only way to adjust rebound on those forks is with oil weight. As you notice, there's no rebound adjustment present.

My neighbor just picked up a 95 that had the forks done by someone. He was told that one fork now controls rebound, and one controls compression. I asked him to show me the paperwork, and he said he has it. I'll see if I can get my hands on that and see what was done, might help you out.... I wouldn't hold my breath though. It sounded to me like a crock.
User avatar
SS109
KDXRider.net
KDXRider.net
Posts: 5770
Joined: 05:11 am Aug 23 2009
Country: USA
Location: Tucson, AZ, USA
Contact:

Post by SS109 »

>|<>QBB<
juliend wrote:
I am very happy with the stock forks on my '04 KDX
Now there's something you don't hear very often!
Well, I actually miss my stock forks! They were much better in the sand and the tight twisty stuff than my current stock KX forks. Once I get them re-valved though I'll probably think differently.

gregp, probably the best thing you can do is installing some Gold Valves. You could adjust your rebound with your fork oil and then tailor the Gold Valve for proper compression using that oil.
Youtube Channel: WildAzzRacing
AZ State Parks & Trails OHV Ambassador - Trail Riders of Southern AZ
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
'11 GasGas EC250R
User avatar
Julien D
KDXRider.net
KDXRider.net
Posts: 5858
Joined: 07:53 pm Nov 07 2008
Country: USA
Contact:

Post by Julien D »

I wont' argue with that. When the trails get really rough and rocky, and the going is slow, I kind of miss my old forks too sometimes. They soaked all that stuff up instead of bouncing around like the mx forks do. The benefits much outweigh that though. I like being able to ride faster without fearing for my life, lol.
Image
KarlP
Supporting Member III
Supporting Member III
Posts: 1484
Joined: 02:26 pm Jun 29 2005
Country:
Location: Alabama

Post by KarlP »

I would try a hevier weight oil, say 7 wght. It may not effect the compression damping in a bad way. If you are already in that weight range a revalve would be needed....

I found the KX forks (as well as CR suspension) needed to be revalved for the KDX. I fought it for a while but that is what I ended up doing in the end.
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Post by gregp »

Thanks for all of the comments so far. I am not looking for the non-existant "adjustment". I am looking to make a modification to my fork damper rods, such as weld up the rebound port, and re-drill another one, in a smaller dimension.
I ride tight gnarly trails with high speed, sharp hits, and the stock forks really work fairly well. I have tried many different oil weights, and just want to custom tune them to my preferences.
To tell the truth, I have ridden many more recent bikes with USD forks, and most stock items do not work as well for me. I have ridden some bikes with modified forks (for Eastern conditions) from Factory Connection, C-Cycle, and more, and some work very well - but all that work well seem to have very minimal compression damping characteristics, with a significant increase in rebound.
At sme point, I may consider Gold Valves, or machining my own "large port" pistons, but for now, I just want to look into the increase in rebound damping. I have found that revalves help, but there is no overcoming restrictive ports when it comes to sharp hits.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Post by gregp »

>|<>QBB<
juliend wrote:
I am very happy with the stock forks on my '04 KDX
My neighbor just picked up a 95 that had the forks done by someone. He was told that one fork now controls rebound, and one controls compression. I asked him to show me the paperwork, and he said he has it. I'll see if I can get my hands on that and see what was done, might help you out.... I wouldn't hold my breath though. It sounded to me like a crock.
That sounds very interesting. I am certain that it not as simple as flipping one base valve over, as the oil in that leg would need to bypass it during the compression stroke....
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Post by gregp »

H series rebound adjuster "kits" can be found here:
http://www.racingsuspensionproducts.com ... vekit.html
It looks like the are installed inside the damper rod itself, and use YZ85 caps and rods... I am looking to accomplish the same thing, in a simpler, non-adjustable way.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
User avatar
ihatefalling
Supporting Member
Posts: 410
Joined: 09:30 am Jul 20 2008
Country:

Post by ihatefalling »

I'm not a suspension expert my any means. I too enjoy the ride of my 05. It has gold valves in it. They were there when I bought the bike. I've ridden newer bikes with USD suspension. They do seem harsher to me although, I didn't get to ride them long enough to get comfortable with the bike and ride it at anny great speed on singletrack.

It sounds like you do a lot of riding like I do.

By "more rebound dampening" you mean you would like to slow down the rate at which the front forks "bouce back"...right? Can you explain why you would want that? Maybe it would be good for me too....

Do my gold valves offer rebound dampening?

Can you "dumb down" what the "kit" does? Would it work with my gold valves?

The extent of my suspension mods/knowledge are....the bike came with gold valves in it. I switched from 5 weight oil to 7.5 weight oil and liked the difference. I've wondered if I would like a heavier 10 weight oil.

Thanks....
2005 KDX 220
R&B Carb Mod
R&B Head Mod
Fork Swap - 99 KX125 Valved for B woods plush
FMF Gnarley
Airbox Mod
Tagged
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Post by gregp »

This is all a matter of personal preference. Yes, I want to slow down the rate at which the forks extend. I want this because I run very light oil to reduce compression damping. In turn, this allows my forks to spring back up too fast, which can cause loss of control, or unintended wheelies.
I owned a KLX250 with Gold valves installed, but I never had them out to look at them (shame, really, laziness on my part), so I do not know if you could adjust the rebound damping with them by shuffleing the shim stack on the rebound side. By looking at them, I would guess "not very much". The biggest advantages of Gold Valves are the extra large compression ports, which means that they can blow off sharp, high speed hits more effectively. I believe that you will find the rebound ports slightly smaller, or very similar in area to the ports in the original valve, and it would not be externally adjustable at any rate.
Gold valves will allow you to run heavier oil than I do, increasing rebound damping, while still allowing a somewhat plush ride.
Gold valves are definately the way to go, but I am trying to find a "free" solution. I suspect that there is none, but that will not stop me from experimenting.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Post by gregp »

As far as the USD fork conversions go, the thing you gain is rigidity, and steering accuracy. You will still be restricted by compression port size in almost all stock MX forks. MX bikes are just not designed to hit the same types of things that trail riders hit. So, even with KX forks, I would most likely end up looking at doing the same thing (been there, done that - CR's and KTM's).
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
User avatar
Mr. Wibbens
KDXRider.net
KDXRider.net
Posts: 4884
Joined: 02:57 am Nov 07 2004
Country:
Location: Playing in the Poison Oak
Contact:

Post by Mr. Wibbens »

Best thing I ever did for my bike's handling was got up to 10w in the forks. Really slowed em down. I can now ride steep rocky or rooty sections that I used to get off and bulldog the bike through
Warning! This member tends to use sarcasm as a regular form of communication. If a post seems offensive, before you panic and fly off the handle, re-read the post and imagine it being said with a sideways grin.
((Bike Profile))
((Pics))
FIVE OUT OF FOUR PEOPLE DONUT UNDERSTAND FRACTIONS
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Post by gregp »

Ah, this is exactly what I am after, Mr. Wibbens, except I want to use very thin oil and still obtain that result. I have worked on many cartridge design forks, but the KDX items are a bit primitive by comparison. Upon cursory examination, it did not appear that the cartridges themselves were easily disassembled for access to the cartridge piston. On the conventional cartridge forks on my old 1987 CR250, the cartridges were very similar, and the hole at the top of the inner cartridge rod was the orifice that regulated rebound flow. When I pumped the CR cartridge up and down, oil would come squirting out. I have not had the pleasure of having the oil squirt out of the upper hole in my KDX cartridges (all over my shirt), but I will take them apart and see what I can find out. It seems that it would be an easy process to weld up these little holes, and re-drill much smaller ones, to get the effect I am after, if they do indeed regulate rebound oil flow. I would also suspect that the piston inside the damper cartridge is a "rebound only" valve, much like the base valve is a "compression only" valve.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
User avatar
SS109
KDXRider.net
KDXRider.net
Posts: 5770
Joined: 05:11 am Aug 23 2009
Country: USA
Location: Tucson, AZ, USA
Contact:

Post by SS109 »

Good luck with it and please post up your results. You might just be on to the next "cheap" mod for the stock forks that others may benefit from.
Youtube Channel: WildAzzRacing
AZ State Parks & Trails OHV Ambassador - Trail Riders of Southern AZ
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
'11 GasGas EC250R
User avatar
Indawoods
Creator and Founder
Creator and Founder
Posts: 9951
Joined: 09:59 am Jun 12 2003
Country:
Location: Midwest

Post by Indawoods »

The old school of thought on the stock KDX forks was to remove a few of the larger shims... now I have no idea why this is but people swore by it. Just throwing it out there for those why remember why or have done it.
*** Administrator //***
****'95 KDX 200/****

"People ate cows a thousand years ago for the same reason we eat them now. Cause they are easy to catch.We're not savages,we're just lazy. A cheetah could taste like chocolate heroin. But will never know. Those bastards are fast!!! "
gregp
Member
Posts: 498
Joined: 03:44 pm Jul 30 2009
Country:

Post by gregp »

Inda - I have already performed that mod - but all of the shims on our base valves are the same size and thickness. I did remove two of them, though (two from each side), with no discernable improvement to speak of.
I will let you all know what I find out by experimenting.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
User avatar
ihatefalling
Supporting Member
Posts: 410
Joined: 09:30 am Jul 20 2008
Country:

Post by ihatefalling »

>|<>QBB<
Mr. Wibbens wrote:Best thing I ever did for my bike's handling was got up to 10w in the forks. Really slowed em down. I can now ride steep rocky or rooty sections that I used to get off and bulldog the bike through
Alright Wibby....just drained the atf out of the forks and put in 10 weight. Riding singletrack Saturday. Hoping I'm like you and really like the 10 :cool:
2005 KDX 220
R&B Carb Mod
R&B Head Mod
Fork Swap - 99 KX125 Valved for B woods plush
FMF Gnarley
Airbox Mod
Tagged
ez
Member
Posts: 26
Joined: 10:42 pm Sep 26 2010
Country:
Location: NC

Post by ez »

very interesting thread seems like the forks are everyones complaint.I am curious what is the weight of the factory fork oil? thanks
jumping is no problem however landing is another story
User avatar
Indawoods
Creator and Founder
Creator and Founder
Posts: 9951
Joined: 09:59 am Jun 12 2003
Country:
Location: Midwest

Post by Indawoods »

Pond Scum.... whatever that is.....
*** Administrator //***
****'95 KDX 200/****

"People ate cows a thousand years ago for the same reason we eat them now. Cause they are easy to catch.We're not savages,we're just lazy. A cheetah could taste like chocolate heroin. But will never know. Those bastards are fast!!! "
Post Reply