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Old 12-26-2006, 05:29 PM   #1
Zerodog OP
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Location: SLC, UT
Oddometer: 1,233
Cool2 Check out my stacks---Zerodog's fork mods

Here is the mods I came up with for my 03 640A. The problems it had were, a harsh ride on dirtroad washboard without subtanks and very open compression clickers. But even though it was too harsh on small stuff the fork was very divey on downhills and braking. The plan was a beefed midvalve and lighter 2 stage basevalve. The idea was to keep it high in the stroke but suck up small bumps like gravel and washboard easy.

On this list I use 1 instead of .1 and 1.5 instead of .15 for the thickness
This is for use in a graph I am working on. If I get it worked out it will be cool to help visualize valve stacks.

Stock 640 Adventure Fork

Base Valve
6 24 1
2 20 1
2 18 1
16 1.5
14 1.5
10 3
18 2.5

Midvalve
4 24 1
22 1
20 1
18 1

.7 stack
1.8 float

Rebound
5 Delta24 1
20 1
18 1
16 1
14 1
10 3
16 3

100mm oil height ?wt from previous owner



Mods 12/24/06

Base Valve

2 24 1
12 1
24 1
22 1
20 1
18 1
16 1
14 1
12 1
10 3

Midvalve
3 24 1
22 1
18 1
14 1
10 1
12 1
14 1
20 1.5
2 10 2

1.45stack
1.13float

Rebound
4 Delta24 1
20 1
18 1
16 1
14 1.5
10 3
16 3

100mm Oil height 5wt oil


So what did it do?

On my initial test riding around town. (No Offroad yet) It seems to be better on square edge bumps like manhole covers and pot holes. Before these were jarring to say the least. The subtanks made this kind of hit better but then it is too soft for me on the street. With the heavier midvalve it does ride higher in the stroke. There is a lot less brake dive. I have to really stab the brake to get it to really dive hard. But it still has 4-5 inches left. With the old valving I could almost bottom it. On dips between streets and into parking lots the fork Gs out a lot less too. I went to a school that has a series of speed bumps. It felt good but nothing surprising. I was mostly impressed with my curb test. (Driving straight into a 6inch curb like it isn't there.) First 10mph. The fork moves and sucks it up nicely. No harshness. 20 mph. Even better. I didn't even lean back. It just sucked it up. I think the curb would have popped my tire with my old setup. It just feels very progressive. All testing today was done with the tanks off. I can't wait to get it on dirt. This weekend will be the test. Desert Whoops here I come!

Zerodog screwed with this post 12-26-2006 at 06:01 PM
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Old 12-26-2006, 06:18 PM   #2
creeper
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Location: Puget Sound
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Quote:
Originally Posted by Zerodog
Here is the mods I came up with for my 03 640A. The problems it had were, a harsh ride on dirtroad washboard without subtanks and very open compression clickers. But even though it was too harsh on small stuff the fork was very divey on downhills and braking. The plan was a beefed midvalve and lighter 2 stage basevalve. The idea was to keep it high in the stroke but suck up small bumps like gravel and washboard easy.

On this list I use 1 instead of .1 and 1.5 instead of .15 for the thickness
This is for use in a graph I am working on. If I get it worked out it will be cool to help visualize valve stacks.

Stock 640 Adventure Fork

Base Valve
6 24 1
2 20 1
2 18 1
16 1.5
14 1.5
10 3
18 2.5

Midvalve
4 24 1
22 1
20 1
18 1

.7 stack
1.8 float

Rebound
5 Delta24 1
20 1
18 1
16 1
14 1
10 3
16 3

100mm oil height ?wt from previous owner



Mods 12/24/06

Base Valve

2 24 1
12 1
24 1
22 1
20 1
18 1
16 1
14 1
12 1
10 3

Midvalve
3 24 1
22 1
18 1
14 1
10 1
12 1
14 1
20 1.5
2 10 2

1.45stack
1.13float

Rebound
4 Delta24 1
20 1
18 1
16 1
14 1.5
10 3
16 3

100mm Oil height 5wt oil


So what did it do?

On my initial test riding around town. (No Offroad yet) It seems to be better on square edge bumps like manhole covers and pot holes. Before these were jarring to say the least. The subtanks made this kind of hit better but then it is too soft for me on the street. With the heavier midvalve it does ride higher in the stroke. There is a lot less brake dive. I have to really stab the brake to get it to really dive hard. But it still has 4-5 inches left. With the old valving I could almost bottom it. On dips between streets and into parking lots the fork Gs out a lot less too. I went to a school that has a series of speed bumps. It felt good but nothing surprising. I was mostly impressed with my curb test. (Driving straight into a 6inch curb like it isn't there.) First 10mph. The fork moves and sucks it up nicely. No harshness. 20 mph. Even better. I didn't even lean back. It just sucked it up. I think the curb would have popped my tire with my old setup. It just feels very progressive. All testing today was done with the tanks off. I can't wait to get it on dirt. This weekend will be the test. Desert Whoops here I come!
Interesting stuff Rob... looking forward to a more complete review of your impressions, when you get the chance.

Something that might be of value to others is your weight, approximate riding ability level or terrain/speeds you encounter, fork spring weight and approximate shock set-up... as a point of reference.

That "curb test" thing you speak of... you must video tape that.

C
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Old 12-26-2006, 07:53 PM   #3
Zerodog OP
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I will try to video the curb test this week. I will do 10, 20, 30+mphshots. This is winter urban suspension testing at its best.

Other info as requested by the Creeper man:

Rider weight 190 Ability-advanced trail rider...at least on a real dirtbike.
Terrain mostly ridden. (pretty much the full range of what a 640 could encounter) loaded, unloaded and even 2 up offroad. Roads, desert dirt roads and trails. Then in the summer, mountain dirtroads, jeep trails, and singletrack.

Basic fork setup
front springs 5.0s
rear 8.0
Fork clickers
Rebound 6 out from fully closed
compression 7 from fully open...I think?

Basic shock setup
Revalved shock by Trail Trick and me.....soon to get more work by me.
Around 110mm sag
7 compression... needs some more low speed or maybe some more preload on the spring.
8 rebound......needs some more high speed for big g outs when loaded down(with my GF on the bike)
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Old 12-26-2006, 08:02 PM   #4
creeper
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Location: Puget Sound
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Groovy Robski...

That should give everyone a base line from which to work something out for themselves.
Or, if they don't know which end of a wrench is which don't feel confident doing the work themselves, they can send their forks to you I bet... and for a reasonable fee, you'll hook them up yes?

Don't forget them crash curb shots!
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Old 12-27-2006, 01:49 AM   #5
bmwktmbill
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Zerodog and all,
Let me be one of the first to thank you for sharing your work. You are the only suspension tuner that I know of who is this open with potential customers. We all owe you our respect and we are in your debt. I hope this forum can continue with the same spirit of openness.
After all, we aren't racers trying to get to the finish line first.
We are all interested in making our motorcycles ride more safely and comfortably.

For those who don't know about the history of suspension tuning, let me say that it is mostly closely guarded secrets, snake oil and bullshit.
There is a guru factor.
Often large sums of money trade hands and the results for the riders are mediocre at best.

My '02 Adventure has even more antique suspension than your '03.
I have no midvalve. It consists of a checkplate comprised of 4x24x.1 shims. The float was similar to your stock setup.

I did run a modded basevalve all summer with two 24mm shims on top. There was no problem with durability and it makes you wonder why KTM chose such heavy valving for the stock setups. The basevalve changes were a good first step for me but no substitute for the complete re-valving work you are doing, with testing and reported results.

Don't get going too fast with that new setup. You have to stay healthy.
You are the man.
BTW, +1 on lightening the rebound stack, it might need more??
Bill.
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
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Old 12-27-2006, 08:01 AM   #6
Zerodog OP
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Thanks Bill! The midvalve/ checkplate that was on mine stock isn't a whole lot different then what you are running now. You can build up your midvalve to be the same as what I am running. I filled up full with gas this morning and it still stays up in the stroke. Watching my headlights dip a lot less when I shift let me know that it is moving a lot less under this kind of weight transfer. So I think the midvalve is the answer to the divey mushy action of the 640a. The 640 is so heavy up front that controlling weight transfer is key to making it ride better. I did lighten the rebound on the lowspeed side but I also made it stiffer on the high speed section by adding the thicker 14x1.5mm shim. This helps with the bigger fork motions. This is what I want to do to the shock too. Build up the smaller diameter shims so it helps resist this kind of bobbing on large g outs. I am not sure why manufacters choose such heavy stacks for basevalves. Most guys don't need it at all. But I think to some degree it makes up for heavy riders with the wrong springs. I think the main thing is they try to come up with something that is Ok all around. If they pick any one way to set up a suspension someone somewhere will hate it.
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Old 03-13-2007, 02:46 AM   #7
bmwktmbill
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'02 midvalve substitution for short tap

Z-dog,
Hope the Baja was good.
I got a couple of suspension questions.
My '02 Adventure has the old style tap.
I'd like to make them work.
I measured the midvalve space carefully with the spring and shims out.
It was 1.96mm.

That makes me a little short on your complete midvalve. I don't want to space the nut out much more because it was peaned over as a safety measure to lock it in place. That seems like a good idea to me. The nut is right at the end of the threads with this measurements and tight.

I was thinking I could substitute 1-24x.15 for 3-24x.1. Are they equivalent?
That would leave me a float of 1.06 with the rest of your stack.
My '02 midvalve would be:
1-24x1.5
1-22-.1
1-18x.1
1-14x.1
1-10x.1
1-12x.1
1-14x.1
1-20x.15

So mv space is 1.96mm.
Stack is .9mm
Float is 1.05mm.
What do you think?
Should I order the updated spring for the '03 tap? It's cheap.

BTW I unscrewed the taps to clean them. That was a bad job and needed heat to release the red threadlocker. After a good cleaning they work much more smoothly. The needles were hanging up in the bores.
I am going to order new o-rings just in case the guy that was in there before me used a solvent that expanded them.

Somewhere in my notes I have a shim substitution guide.
Do you have it handy

This is so fun,
Bill.
__________________
'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley

bmwktmbill screwed with this post 03-15-2007 at 01:03 AM
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Old 03-13-2007, 04:50 AM   #8
Luke
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Quote:
Originally Posted by bmwktmbill
Somewhere in my notes I have a shim substitution guide.
Do you have it handy
Try here, the shim substitution guide is the third from the bottom of the list.

According to this, 1 .15mm shim is equivilent to 3.4 .1mm shims.
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Old 03-14-2007, 05:04 AM   #9
bmwktmbill
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bump

Hey Luke,
Thanks for the link.
Now where to find a 24x.15 shim. Maybe MXtech
Bill
__________________
'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley
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Old 03-14-2007, 06:38 PM   #10
Zerodog OP
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I think that would work Ok. That is a lower float than what I am running now. My float is 1.13. The 03< midvalve spring might be a good thing or a bad thing with that midvalve. If it is lighter that could be good. Then it blows open easier on the small bumps. So it looks like you didn't need the 10mm shims on the back of the stack to get the float down. The 02 must have a longer shoulder than the 03. MX-Tech is a good bet for the shim you need. I will look tonight and see if I have some.
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Old 03-14-2007, 08:19 PM   #11
alpiv
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does anyone have the shock stack for the stock shock on an 03 Adv?
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Old 03-15-2007, 08:51 AM   #12
Zerodog OP
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Quote:
Originally Posted by alpiv
does anyone have the shock stack for the stock shock on an 03 Adv?
I have them on my computer at home. I can post them for you when I get a chance.

Bill, Keep in mind soft springs don't always mean plush. Soft springs will give a harsh ride if there is too much weight to support and the suspension blows through its stroke.
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Old 03-15-2007, 01:26 PM   #13
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You rock
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Old 03-15-2007, 01:19 AM   #14
bmwktmbill
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Thanks For looking/commenting on the stack Z dog.
The 24x.15 is just a little heavier than three 24x.1. If I combine it with a little lower float and the soft mv spring it might be OK for the gravel especially because my bike is lowered and I don't have as much fork travel as the stock machines, the stiffer mid valve might be the right diagnosis especially if my fork springs are a little soft.

I keep thinking PLUSH, whatever that means. Suspension tuners throw that word around.
I want plush....
Bill
__________________
'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley
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