Motoman, EGO, other suspension experts, I have my forks apart need you opinions



33 replies to this topic
  • armourbl

Posted July 29, 2002 - 06:38 AM

#1

First off,

Thank you Motoman393 and Ego. With your help I was able to take apart my forks this past weekend. I have lots of fun stories to tell you all, but I need some advice first...

You may remember, I've already put the 426 springs in my WR250. Forks .46, Shock 5.2. Now I'm installing the stock 426 vavles.

Here are my shim stacks. I need to know if you all think that this is correct. YZ426 valve piston, 2-stage compression stack.. () = quantity, mm = diameter. Listed in the order installed...

Slow speed stack
(2) 24mm
(1) 22mm
(1) 20mm
(1) 16mm
(1) 11mm

High speed stack
(3) 24mm
(1) 22mm
(1) 20mm
(1) 18mm
(1) 16mm
(1) 14mm
(1) 13mm
(1) 12mm
(2) 11mm
(1) 18mm

Dampening. Mid-valve converted to Check-valve.
(2) 27mm
(4) 24mm
(1) 12mm
(1) 19mm
(1) 18mm
(1) 16mm
(1) 14mm
(3) 11mm

I need to know if I have the orders correct. I tried to add a consistant amount of shims to allow the retaining nut to seat flush on the threads.

For the compression stack I tried to use Race Tech's recommendations as to what order to put the shims. On the dampening stack I just tried to use the same order that the stock valves stack had, but added a few more shims to make up the space created by converting the mid-valve.

Do I have it right? Forks are still apart until I can get some kind of confirmation that I have the shim stacks correct.

ben

[ July 29, 2002: Message edited by: armourbl ]

  • John_Lorenz

Posted July 29, 2002 - 06:46 AM

#2

First

I would have to look at me notes, unfortunatly they are at home and I am not.

Second
It sounds as though you have it correct, butto be safe I would call mx-tech or Race-Tech to confirm. Seeing as you have swapped the springs and valves out I am not sure.

Sorry could not help any further
Good luck

  • armourbl

Posted July 29, 2002 - 08:18 AM

#3

Friendly bump..

Oh yeah, Ego, you bolt idea worked great on getting the bottom valve stack out. I looked all over town for a 14mm allen socket, but no one had one. Then I remembered your idea. It worked out great.

Motoman393's website and homemade tools also worked well. The Race Tech instructions he posted on his site in a .pdf format were a life saver when it came to building the new shim stacks.

Thanks again guys...

Still looking for more opinion on the above posted shim specs..

ben

  • DaveJ

Posted July 29, 2002 - 10:47 AM

#4

armourbl,

You're right about the 14mm not being a standard item. I had to order one off of Snap-On.com.

As for your fork configuration, it looks like a good trail set up, assuming of course you're also running the restrictor plate under the cylinder valve.

Shim stacks will vary based on a rider's need and the feel they wish to have. You may want to try some combinations if you have the energy for it.

If you wish to get serious about jumping or doing some track work, let me know and we'll have a chat about that mid-valve.

DaveJ

  • armourbl

Posted July 29, 2002 - 11:02 AM

#5

I'm not running the cylinder seal. All I'm changing is the shims and pistons from the YZ426.

DaveJ, please share with me any info or opinions you may have. I do plan on riding MX and a major reason for the changes in the valving is to correct my suspension for MX.

ONE MORE VERY IMPORTANT QUESTION....

I had to drill the punch marks on the cylinder to remove the cartridge. In Race Techs instructions it says to avoid drilling all the way through the cylinder wall, but I had no choice -- the damn thing wouldn't budge. So, is having the punch marks drilled out completely going to affect anything? If yes, how do I correct it?

ben

  • Scott_F

Posted July 29, 2002 - 01:39 PM

#6

How big are the holes, and how deep did you go into the cap? As long as they don't leak, you will be ok.

  • motoman393

Posted July 29, 2002 - 01:45 PM

#7

That stack looks OK. Im not sure the stack you posted above is the same as the stock 426 though (I remember someone posting it on TT about 5-7 months ago), I will measure my stock stack after I eat dinner and post it here.

About drilling out the peening. You went all the way through the cartridge walls when drilling :) ? You only need to go just far enough to release the peening. I had to heat the cartridge up with a propane torch to get mine to come off (but be careful you dont damage the coating on the damping rod)

You mention the diameter and quantity but dont list the thickness like: 18 x .10 x 3 or 18 x .15 x 3 etc. what size are you using? Good Luck,

Garrett

  • DaveJ

Posted July 29, 2002 - 02:28 PM

#8

Ben,

You don't have to drill all the way through the cartridge tube in order to relieve the peen enough so that the cartridge valve can be removed.

However, not drilling enough can cause damage to the threads of the both the tube and valve if the valve is forced out.

So....many of the suspension guys will set a depth gauge and go off that, or they have done it so many times they know what feels right.

Now....on the tubes that I have drilled to what I think is a minimum depth, I have found that the cartridge tube pressure, over time, will cause the machined area to burst and leak. Sometimes the leaking can release substantial amounts of fluid causing very poor fork and front-end performance, especially when one fork leaks really bad and the other one doesn't.

This leads to the lesson that anytime you disturb a design going in, you have to reconsider the design on the way out.

Furthermore, this tends to a fork that will perform well for a short period after the service, then rapidly deteriorates as the holes open up.

This is perhaps, a major oversight in the Race-Tech procedure. Unfortunately, many shops are also unaware of this. However, just because I had this problem, doesn’t mean that everyone else does.

Soldering or filling the holes is not an option. Applying sealant to the cartridge valve threads helps, but does not fully seal or last long enough.

The only option is to run an o-ring assembly down past the holes, so that the oil pressure is directed into the cartridge valve or passed the bushing.

With no mention, the restrictor plate offered by Race-Tech does this. However, they don’t spec it for this reason.

If you run bottoming cones, they include a spacer with an o-ring to keep this from occurring.

I’ll be back later to talk about some other issues.

DaveJ

[ July 30, 2002: Message edited by: DaveJ ]

  • armourbl

Posted July 29, 2002 - 04:36 PM

#9

OK,

THEN I'M OFFICIALLY SCREWED. !@#$%^&*(

I drilled all the way through. I tried and tried to loosen the damn thing, but it wasn't until I drill through completely that they came loose. So now I screwed. Will a lot of loc-tite work? (I'm laughing and crying all at the same time here)

Funny thing is, if a shop accidently drilled all the way through, I doubt they'd admitt to it. So what do they do?

Garrett, I'm assuming that the shims are all 10 hundredths of a millimeter thick. I have no accurate way to measure the thickness.

I'm looking at the Race Tech Valve Compression Chart again and I'm re-thinking my stack. Can you recommend which CL and CH to run for a 190 without gear, 6'1" fit frame. WR250, 426 springs, .46, 5.2.

Guys, please get me through this, I'm sweating ball bearings here..

ben

  • Scott_F

Posted July 29, 2002 - 05:31 PM

#10

Ben, don't let Dave scare you too bad. Your forks will still work. I do recommend the bottoming cones though. And Dave, tell him how to check for leakage.

So Ben, just how big and deep are the holes?!? Did you bugger up the caps?

The real flimsy flexy shims are .10mm. The thicker ones get progressively stiffer.

You need to buy a digital caliper. They are very cheap now. I bought a spare one at Harbor Freight for only $20 on sale.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • motoman393

Posted July 29, 2002 - 05:48 PM

#11

Ben,

I am running cL5 cH2. I am about 180lbs it works very well for me. But I have RT's valves... since you still have stock valves I dont know how it would work since RT's port sizes are larger.

I was soooo frustrated when I was revalving my suspension the 1st time. Dont worry you will make it through and when it is all said and done, you will be glad you did it! Keep us updated on your progress.

Garrett

  • armourbl

Posted July 29, 2002 - 06:07 PM

#12

Ok, Read toward the bottom for more info on the cartridge tube drilling issue...

After thinking it through with my own logic and the RT chart for some kind of base, I've changed my valve stack.

Slow speed stack
(4) 24mm
(1) 22mm
(1) 14mm
(1) 12mm

High speed stack
(3) 24mm
(1) 20mm
(1) 18mm
(1) 16mm
(1) 14mm
(1) 13mm
(1) 12mm
(2) 11mm
(1) 18mm

Dampening. Mid-valve converted to Check-valve.
(3) 27mm
(4) 24mm
(2) 20mm
(1) 18mm
(1) 16mm
(1) 14mm
(3) 11mm

These are all the stock shims, and although this seems weird to say, I can actually tell the difference in the thickness by feel alone. I can tell what is thicker and thinner, at least I think I can. I know we are talkin pubic hairs here, but I'm pretty sure that the majority are all the same thickness. This is especially true of the shims with the smaller shaft (inner) diameter. The shims with the larger shaft diameter have more noticable variances in thickness.

Now for the cartridge tube drilling issue...

I guess at this point my biggest concern is the holes in the cartridge tube. I only drilled just as far as necessary to go clean through. I didn't damage the cap threads at all.

Should I be worried. Will a lot of loc-tite prevent leaking. Any other miracle fixes I can perform?

I feel really good about the valving. Hopefully it will perform well.

I am a bit disappointed in the pistons though. Close examination, (basically eye-balling them) the 426 and the 250 pistons look identical. Which means I paid $50 for shims and an extra set of pistons... :-(

ben

  • armourbl

Posted July 29, 2002 - 06:17 PM

#13

Thought you guys might be interested in comparing the stock shim stack on the WR250F.

These are listed in order starting from the piston face because I don't know where the low and high speed stacks begin and end on the stock stack.

piston
(4) 24mm
(1) 22mm
(1) 20mm
(1) 9mm
(1) 16mm
(1) 18mm
(1) 11mm
(1) 18mm

Mid-valve
(3) 11mm
(3) 27mm
(1) 12mm
(1) 20mm
(1) 18mm
(1) 16mm
(1) 14mm
Piston
(3) 27mm
(1) 20mm
(1) 16mm
(2) 14mm
(1) 25mm
curved cap
retaining nut

Not very agressive from what I can tell. Just thought you guys would like to see why the stock suspension is so soft.

ben

  • DaveJ

Posted July 30, 2002 - 06:00 AM

#14

Ben,

Here's some more info for you.

First, you have not damaged your forks. My point was to let you know that drilling the forks at any level (depth) opens the possibility of leakage.

To test for this, you can take an assembled cartridge tube, screw in the bottom valve assembly, (compression piston) and then work the rod up and down in a bowl of fork oil. This simulates what is taking place inside the fork.

Any oil that is coming from the holes should really be moving into the cylinder valve or compression valve. If 2 holes leak on the left fork, and four leak on the right fork, you won't have much suspension.

With that, I'm not sure if I have a solution. Lok-tite is an adhesive and really doesn't have sealing properties. Silicon gets blown out.

I tried an epoxy once, but with little bite and the constant breakdown from pressure and oil, it too gave way.

I was only able to resolve this when I ran an o-ring plate beneath the cylinder valve. Then when I switched over to the C-Cycle bottoming cones (www.ccycle.com) their design has a spacer with an o-ring to resolve this issue.

So I think I feel fairly confident in saying that anyone that has drilled these holes is potentially going to have this problem. Just at different degrees.

DaveJ

  • armourbl

Posted July 30, 2002 - 06:23 AM

#15

Well,

I called our local Race Tech shop and spoke to the owner. He kind of laughed at me, but in a supportive way and told me that he did the same thing on the first set of forks he worked on years ago. He said if I run the Race Tech Cylinder Seal that I won't have any problems.

So, I'm off to his shop later today to get the seals. Approximately $35 for the pair.

I'll let everyone know how it goes.

ben

  • DaveJ

Posted July 30, 2002 - 06:24 AM

#16

Now the next issue - the mid-valve.

As I understand it, the mid-valve was designed into this fork to dampen or "flatten" the compression curve. Meaning that it was to provide a more plush, yet feel firm particularly during rapid or high compression movements.

You could also relate this to rod speed, meaning that the mid-valve was designed to keep the compression rod from traveling within the fork at a high rate of speed. This helps to keep the fork within a mid-range of the suspension travel.

However, the mid-valve on my 00 426 made the fork feel tight during high compression movements. When riding rocks or fast downhills, my hands and upper body got beat.

Other users also complained that the mid-valve would fail, since the valve stack was taking so much abuse that the shim stack was bending and becoming damaged or fatigued over time.

I too had this problem but not as severe as others.

The fix within the business was to place a backing washing on the top of the stack, so that the mid-valve stack would flow oil, but not distort the shims. The mystery was how close the backing plate should be to the shim stack so as to allow enough oil flow without causing too much restriction.

As for removing the mid-valve, I think it works only if you run a restrictor plate at the top of the cylinder valve. Race-Tech is the only company that I know of that sells these with their kits or separately.

This combination works fairly well for most trail riding, but soon as your speed increases or your riding needs become more aggressive, you'll find that that the purpose of the mid-valve is an integral design with this fork.

Meaning, that without the mid-valve, you lose too much of the balance that exist between all of the valving circuits. The fork feels good at low speed, but moves around too much when you start riding fast.

I tried many configurations to get the fork to work without it, but I ended up reinstalling it with a backing plate. Now I'm attempting to determine how much float I can and cannot get away with as well as a proper mix between the mid-valve and compression shim stack.

I'm so far into my design, that it’s practically becoming a proprietary fork.

PM me your number if you want to discuss this further.

DaveJ

  • armourbl

Posted July 30, 2002 - 06:50 AM

#17

Good stuff DaveJ, lets keep the information flowing please.

Along with the cylinder valve seal, I'm going to try to pick up the Race Tech Check Valve Plate. That is, assuming that the check valve plate isn't just a simple shim, but rather a stronger, thicker shim.

I imagine that this won't be the last time I have my forks apart to tinker with the valves and shim stacks. So, I'm going to give the mid-valve conversion a try.

Everyone seems to agree that the stack that I've decided to run will function correctly, so I guess I'm headed in the right direction.

I feel like an idiot for attempting to do this before a big trail ride trip to Colorado scheduled for the second weekend in August. If I don't get this right, or screw it up terribly, it could end up meaning I don't get to go on the trip.

ben

  • armourbl

Posted July 30, 2002 - 07:43 AM

#18

Just thought I'd point out that www.ccycle.com has a shock demo quicktime movie illustration that demonstrates who the shock works. This demo really helps me to understand how the shims work to flow oil. You can see how they bend and flex. With this demo you can see how adding more shims in certain areas will affect the stiffness of the dampening and rebound.

ben

  • DaveJ

Posted July 30, 2002 - 09:30 PM

#19

Ben,

If you have a fax number, I can send over some stacks that C-Cycle gave me for standard, enduro and pro configurations.

You can then compare these with other stacks.

DaveJ

  • armourbl

Posted July 30, 2002 - 10:10 AM

#20

Just PMed you with it.

ben





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