What tools for opening cartridge on Kayaba 48 open cartridge?

Hi guys,

What tools are you using to disassemble the cartridge on the 48mm Kayaba open cartridge forks on the later model WRs? Supposedly they are the same base model as later model Yamaha WRs.

Thanks,
Fred

Bump.
Race Tech nor Motion Pro have them.

Not sure if this is what you are looking for: http://www.ziptyracing.com/fork-tools-2/
If not, give us a call.

See page 5 of this thread: http://www.cafehusky.com/threads/diy-tuning-the-sachs-shock.23893/page-5

I made two tools; one tube clamp to hold the cartridge, and one "wrench" to twist the top off. However, I have heard of guys doing it without making any special tools. In theory, you can hold the bottom of the cartridge with a stout rod through the base valve ports, and unscrew the top with an adjustable wrench on the flats under the spring seat.

It is factory glued with loctite, so you'll need a decent bit of heat to break that. Don't melt the shaft seal when you're heating it.

Just for general info, the forks are VERY similar to the forks in my buddy's mid-2000s Yam WR450, and I think they are also the same as early 2000s KX250s. I did my other buddy's mid-90s KX250, and those forks were very similar as well. These are a pretty common design, good forks if they are a bit old tech.

Good luck.

P.S. The tools that Tinken posted a link to will not work on the open cartridge KYB forks on the WR. Those are for the CC forks (like a TXC, CR, etc have). Make sure you double check which forks your particular year & model has, I can't keep track of which bikes got what.

Super thanks for the input. Will try per your instructions.
Many of those earlier Kayaba kawi and yam forks were 47mm and Motion pro has a holding tool for those, which I bought but it didnt fit because the cartridge is now too fat for the holding tool tube.
I'll update with the progress.

Is this not the right tool from RaceTech? TFCH 03

I haven't taken mine apart, but the 48mm KYB open chamber was used in various bikes, I'd be very shocked if they did not have the tool for it.

Hi, sorry for the delay.
The TFCH 03 for "Many KYB 46 & 48mm open chamber forks" $84.99, definitely looks like it should fit, so I missed that one.
The one I got from Motion Pro was "Damper Rod Fork Tool" 08-0117, $36.99 for 41-47mm Kayaba and Showa.
When I bought it it didn't say 41-47mm, I think it said 41mm and larger, or similar.

Just got new shims today to mod the base valve, and hopefully open up the cartridge to have a look-see and document the mid-valve, rebound and float.

Let us know what you find, I'd be curious to see what is in those forks.

Long delay again due to the loctite.
I tried the heat gun to no avail. Did some research and found out alot more heat was needed to melt the loctite, more than 250 deg celcius.
So finally, yesterday was the big success after hitting it with propane for a while and with no special tools.
When I had been at it for about 5 mins I spit on the tube and it sizzled about 1/3rd of the length down the tube.
The loctited thread was about 1cm long on the cartridge tube.
While heating it, I had the cartridge rod about halfway out. At the bottom of the cartridge I put a 6.5mm punch through the 7mm holes that go straight across.
I twisted the billet spring seat off with a regular size polygrip pliers without much force at all, as it there had been no loctite at all.
I let everything cool down and easily disassembled everything.
The mid/rebound piston seems to have a metal ring seal, as opposed to WP that has plastic, maybe due to the heat requirement for disassembly.

So what was in there? But before that I can post what in the base valve first, in order of disassembly.
The bike is a WR125 2011 euro spec and the fork is an open-chamber Kayaba 48mm.
The thickness of the shims is somewhat uncertain since my micrometer is an uncalibrated cheap china model.
Does Kayaba use .11mm shims for their thinnest? When stacking several, it really didn't look like .10, .20, .30, .40 etc.
Can't say for certain for now, it was also late, so everything below might not be 100% error free.
ID = inner diameter, OD = outer diameter.
Here goes, base valve:
Nut 12mm
cup washer (spaceship washer)
spring
bushing
shim ID approx. 11.3mm, OD 25mm x 0.5mm

Valve

(ID 8mm)
24 x 5 x .12
24 x 1 x .15
22 x .12
20 x .15
18 x .12
16 x .15
13 x .15
12 x .12
11 x .25
8.5 x 18 x .5
8.5 x 18 x 1.0
8.5 x 18 x 1.0
11 x .3
24

Rebound/mid valve. Float = 0.75mm, ID 6mm x .1 below if unspecified.
Nut 10mm
regularwasher approx 1mm thick
9 x .2
9 x .2
12
14
16
18
20
22
14
23 x 7

Piston

(ID 8mm x .1 below if unspecified)
24 x 3
22
20
18
16
14
12
10 x .3
10 x .3
22 x .4

I'm a little rusty here, so which is rebound and which is mid valve?

Rebound is on the side with the nut, the midvalve (compression) is on the "top" side, that has the long damping rod coming out of it.

How'd you measure the 0.75mm of float on the mid? Feeler gauges?

KYB thin shims are usually 0.11 mm thick.

Are you positive that all of the base valve shims, including the face shims (24 mm units next to the piston) are 0.15 thick? 6x 0.15 face shims is pretty stiff for a woods/enduro bike...

How do you use the bike, how does it feel now, and what are you trying to accomplish?

Thanks for the input Kyle.

The float was measured with 2 feeler gauges by lightly pulling down the spring-loaded shim stack, which is on the rod side, so it then should be the mid valve.
The forks have one .40 and one .42 spring and a 5.4 in the back to get as close to Vinduro's recommended free and rider sag measurements. I have not messed with the fork preload.
With this float the forks ride quite high in the stroke. Turning could be a bit quicker, but it's fine since I'd rather have longest possible travel in the boulder fields.

I have 13/50 gearing and mostly ride in 2-3rd gear but try to get and stay in 4th as much as possible. The enduro tracks around here are pretty old and worn, so big, exposed rocks and roots are the norm.
We have almost no elevation changes. Acceleration is not that important, it's mostly rolling along with a steady throttle.

In order to re-check all the shims, installed an on inventory, I think I'll get a digital caliper. They claim to have a precision down to .01mm, so it seems they can be used to tell a .11 from a .10mm shim.
Is this realistic?

The goal is to have the suspension on the firm side, but to soften them up to soak up big rocks, extend fast enough to avoid packing or losing contact, having a mid valve that can handle whoops and rollers, and being able to land off jumps.

They have been too stiff, have too much rebound and no good bottoming resistance. Since WP shims are easily and cheaply available I rolled the dice and put in a compression stack with .10mm shims as below:
24
24
16
24
22
20
20
18
16
14
12

This soaked up trail junk alot better, was much better when landing off jumps, but still slightly too stiff. So, I removed one of the 20's and will try that out.
Next will be to lighten the rebound and maybe add a bleed shim.

Happy Easter!

A digital caliper will probably not be able to tell between 0.11 and 0.10 shims; the good news is, this isn't too important. It will be able to tell between 0.1, 0.15, 0.2, etc. To determine exact thickness, you'll really need a micrometer, but for 99% of suspension work I don't think it's necessary.

I'm a little bit confused by your statement(s). You said it's too stiff, but it also doesn't have good bottoming resistance? Are you saying that the forks bottom frequently? What oil level are you running?

I think that your new base valve stack is a good starting point. Usually you'll see more face shims (I am using 4X, stock was 6X), but you'll also see smaller crossovers (mine is 12mm), so those two things probably cancel out. I think the base is probably in the right ballpark, I'd look at the mid and reb.

A few additional suggestions:

-Increase float on the mid (try maybe 0.2mm more float?)
-Remove 2-3X face shims from the rebound. I removed 2X on my bike, but I am running 0.44 springs, so you might want even less rebound damping.

Note that the midvalve damping is the dominant player at higher fork velocities. The amount of damping it creates is very progressive, so at low fork velocities it might only be 10% of the total (with the base valve being the other 90%), whereas at high speeds it can be 75% or more of the total damping. Point being, changing the base is not as effective as changing the mid for certain types of action.

Small tip: you don't need to pull the mid down to measure the float. I find it's easier to just measure the gap between the backer shim (the 22 x 0.4 shim) and the cup washer. Whatever works for you!

I have not done much work with bleed shims myself, I don't love the idea, even though it obviously works in some cases. The way I see it, a bleed shim is more extreme than having a clicker wide open, so if you're not running your clickers wide open and hoping for a lot more bleed...

Good points, thanks. I'll keep them in mind.

Re the stiff but bottoming: they felt unsensitive to rocks and roots but went through the stroke and bottomed on smaller jumps.
I guess the shims needed too much force to bend for my wimpy riding, but once they opened they released the pressure too quickly.
I wanted to try a softer "face" section but stiffer "neck" section on the base valve stack to maintain the pressure.
I tried a quick spin after removing one of the 20's and lessening a click compression in the rear, and it felt promising.

Re the rebound: true, 7 face shims seems overkill and will try going down to 3.
As a bleed, in order for more movement and compliance on small stuff, I was considering a 20 or 18 or something that just leaves a thin opening, but I'll skip that.
The stack is a 2-stage with the 14 crossover, so that might be perfect.

I'll try riding it like that for a while and try to get a feel for how it works over low speed, high speed, balance front-rear, etc.
Once it's good enough, I'll try messing with the rear to get it working in a similar way.

Later, Fred

Yeah, I think you're on the right track. With the stock stack being single stage, it might not open for "trail trash" and will feel harsh.

Keep in mind that bottoming is not just a function of the base valve damping. The midvalve is a big factor here as well, along with the spring rate and the oil level. You're running fairly soft front springs, so that's not helping. I might try going up a bit on spring rate and/or going up like 10mm on oil level, and see how that feels. In my opinion, Vinduro's recommendations for the front end up with slightly too soft springs in some cases, when you need bottoming resistance off jumps.

Just note that higher speed square edge impacts (like rocks, roots, logs, etc at speed) are highspeed damping, so if you make the stack too progressive those can get harsh.

That is quite a large change. I'd start with removing 2 or 3 (try 4 or 5 face shims).

Just keep in mind that a "thin" opening is still a LOT of bypass. Even a 20 x 0.1 mm bleed shim leaves a ring that is maybe 22mm OD and 20mm ID (66mm^2 flow area), which then will flow through a gap that is 0.1mm thick by 24mm diameter (7.5mm^2 flow area). That's the same as a 3 mm bleed hole, which is quite large! The holes for the clicker adjustment are usually 2.5-3mm, so that much bleed is more than double what the clickers have when wide open.

Hi, I have modded the rebound, updated the shim thicknesses above, changed the oil level and some new impressions after having been out a couple of times.
I also edited the gearing, which is stock 13/50 and nothing else for now.

The rebound is now a big success and looks like this now, in order of disassembly:
9 x .2
9 x .2
12
14
16
18
20
22
23 x 2
14
23 x 2
For now, the front wheel seems to track the ground well, without packing and no strange behaviour.

I re-measured thicknesses of all shims from the base valve with a borrowed japaneese professional micrometer from our company lab, and updated the post above.
The shims on the base valve were a mix of .12s and .15s. I tried to bending a .12 and a .15 in my hand and interestingly it seems to be a big difference, the thicker on maybe being twice as strong.
All Kayaba shims in the fork are blue anodized, compare to the WP ones whick are plain metal finish.

I increased the oil level from really low 140mm to 130mm, resulting in action from mid to bottoming ramping up very nice and smooth to a firm but spongy end.

Compression still transmits too much from the big rocks to the bars and I would like the forks to move more.
They also seem to ride quite high compared to the rear.

My average speed of the tested loop is 25kph/15mph and the problem rocks are part of boulder fields, so I guess I'm slowing down some to maybe 15kph/10mph - 10kph/6mph.
The rocks are generally immovable, roundish and can easily be axle-high, most being between 4-8 inches high.
Base valve is right now(.10s):
24
24
16
24
22
20
18
16
14
12

Since the base valve is much easier to get to, I'm considering this:
24
24
16
24
22<-removing this one
20
18
16
14
12

A question regarding the midvalve: can a slow ground speed impact be consideres a mid speed area if the fork action is long, as above?

Any ideas?

You can try to let the oil out, put it bag togheter . Turn it over, bring the spring on tension and you can unscrew the under bolt ( sorry for my bad englich)
Greetz

Thanks husski.
I usually flip the fork upside-down and use an air impact wrench to remove and install the base valve. After installation I need to turn the fork back and remove the top cap and spring to check that the spring guide has not been unscrewed by the air impact wrench.
Later, Fred

Fred-

What are you currently using on the compression side of the mid?

Some of those measurements for shim thickness seem a little bit odd; usually you won't see them switch back and forth between 0.1 and 0.15 thick shims in the stack, you sometimes do see both thicknesses but they're usually grouped together.

The stiffness of a shim is proportional to its thickness cubed; as such, a 0.15 mm thick shim is about 3X as stiff as a 0.1. FYI, KYB shims are usually 0.11 and 0.15 mm thick, not 0.12. It is hard to measure this small of a difference.

That change to the base valve is pretty subtle, not sure it will do what you want. I'd look at working on the midvalve (compression), your base valve is already quite soft.

A low ground speed impact can definitely be mid or high fork speed. It mostly depends on the shape of the feature. A feature with a more "square" shape tends to be higher fork speed than a "rounded" object.

Kyle,
I have a hard time ensuring the thicknesses of the blue shims, since I cannot test the micrometers other than the 0.00 starting point.
Best would be to control against test bits of different thicknesses, but maybe it isn't that important, since in mid and rebound I'm only removing some shims of the same type, and the base is all bare-metal new WP .10 shims.
I bet you are right, the base valve is probably not where to look for increase action, but the relatively stiff mid.

The mid has been unmodified for now and as mentioned looks like this, with the working shims being of unspecified thicknesses for now.
24 x 3
22
20
18
16
14
12
10 x .3
10 x .3
22 x .4

How about removing one of the face shims?
So then the float would increase by the corresponding shim thickness?
If so, I'll need to put in a corresponding 10mm by the .30's?

I really appreciate your insightful info.

I'm considering another longer test run to isolate impressions from different rock types, sizes and speeds, in particular big and sharp ones, and also try to keep the rubber-side down to avoid the wrong kind of impressions :-)

Thanks for now, Fred

I'd bump the float on the mid and leave the base valve where it is (I might actually stiffen the base valve up a bit). I'd bump your float from the 0.75 mm it is now to around 0.9-0.95 mm. The best way to do this is to space the sleeve out on the midvalve shaft with a 6 mm ID shim (OD doesn't matter too much, because the shim will be hidden inside the cup washer). A 6 mm ID x 8 mm OD x 0.15 or 0.2 mm thk shim is "ideal" but anything with an OD of like 14 mm or less will work fine.

If you can't do this, you could remove the 22 mm shim behind the face shims. I'd leave the 3X face shims (I get nervous running less face shims than 2-3). This change isn't as big as I think you might want though. Perhaps remove the 22mm shim and one of the face shims?

I'm not sure what you mean by this last part. You're correct in the assumption that the float will increase by the corresponding shim thickness. I don't know what you mean about putting in a 10 mm shim. For example, if you take a face shim off and put in a 10 mm shim of the same thickness, the float will be the same (but the stack will be slightly softer, which I do not think will help your problem).