To anyone who might be interested, below is the description of the K-Tech modification for the Showa forks on the Monsters (and others) that I promised in the previous topic some time ago. I hope this will be reasonably clear and understandable; I´ll be happy to answer any questions to the best of my abilities.
Cheers to all of you; I´ll be off to celebrate swedish midsummer now
Assuming you know basically how to disassemble and re-assemble the Showa fork, I´ll describe what you specifically need to do in order to convert the Monster-type Showas to proper damping function using the K-tech shim stacks.
Start by ordering a piston kit 20SSK-INT-SHO-3 from K-tech (the picture they provide is not quite exact) : http://www.k-tech.uk.com/product_detail.php?id=1052 This kit is for a 999 fork, and looks slightly different than the kit used for the Monster type forks.
There might be a dealer in your country selling these, if not K-tech will send them to you by mail, I suppose. When the parts have arrived, you can get to work.
If you have the forks in your bike still, start by turning the spring preload all the way out, loosening the top triple clamp to unload the fork top nut, and break the top nut loose.
After you have taken the fork legs off the bike and unscrewed the top nut from the outer fork leg, and pushed the spring / spring spacer out of the way to get at the top nut locking nut on the cartridge rod, carefully loosen the top nut, taking care not to turn the lock nut more than necessary. Screw the top nut completely off the cartridge rod, and measure how much of the rod sticks up above the locking nut. This dimension is important, since it will affect the total available fork travel be a few mm, and it will significantly affect where the rebound adjustment range starts in terms of adjustment clicks; more on this later. Spring preload tube, compressor tool (for the spring), grooved spacer (for locking the spring pre-load tube below the lock nut), and top nut on top of the cartridge rod. This fork is an 848, but it basically looks the same except for the fancy colours.
I now recommend you assemble the fork top nut back on the cartridge rod in the position it will eventually sit when it´s all back on the bike, screw the nut down in the fork tube; NO springs.
Extend the forks as much as possible, and take a measurement to get the max extended length; I measure from the bottom of the outer fork leg to the top of the aluminum part on the lower leg where wheel and brakes go; its easily measured and repeatable. Write down the dimension.
Now compress the forks fully, measure in the same place and write down. This gives you the max. possible fork travel. One leg is enough for this measurement.
Next, use an impact wrench to loosen the bottom screw in the lower fork leg (with the compression adjuster) to get the cartridge out. You´ll need a 19 mm socket with a small outer diameter; a 1/2" drive socket will be too big, but my 3/8" drive socket works just fine. Since your impact wrench will probably be 1/2", you´ll need a 1/2"by 3/8" drive socket as well. You could try without an impact wrench, but it has never worked for me.
Take the cartridge, and do the extended / compressed measurement routine once again; this will tell you if the fork or the cartridge will bottom out first. Hopefully, the forks will bottom out first. Write down for later reference.
Next, go to your drill press and drill out the dimples at the bottom of the cartridge to get the compression stack out. Just drill through the cartrige wall, not down into the compression stack holder.
Screw the bottom nut in a couple of turns, and use a rubber mallet or similiar to knock the compression stack a couple of centimetres into the the cartridge; you now can see the lock ring in the groove in the cartridge; prise it out.
Getting the compression stack assy out of the cartridge can be tricky; at first I used the bottom screw / compression adjuster screw and various suitable washers to pull the assy out of the cartridge; now I have an old compression adjuster screw and a sliding hammer contraption to pull it out. When the assy comes out, it will look a bit second hand, but don´t worry. Showa compression shim stack, shim stack holder, adjuster needle and bottom screw (the adjuster needle is normally inside the bottom screw)
To convert the compression stack with the K-tech shims etc., you need to take the Showa stack off the stack holder. You need a lathe or similiar 3-jaw chuck to hold the shim stack holder or you´ll destroy it. Take out the Showa stuff and throw it away. Or keep it if you´re nervous about this conversion.
Take the K-Teck stack off it´s holder and push it onto an M6 bolt and put a nut on to keep it intact. You´ll need to bore out an M6 allen-head screw and make it the correct length to assemble the the K-tech shim stack on the Showa shim stack holder; the screw from the Showa stack is too short. When you´ve got this done, the compression stack is finished.
Next, you need to get the rebound stack out; it´s at the end of the cartridge rod. Prise out the top lock ring above the white plastic cone on the rod, push off the cone (actually the hydraulic travel limiter), prise out the bottom lock ring as well and push the cartridge rod out of the cartridge. This is the hydraulic travel stop; I throw them away. Te SBK forks I´ve worked on do not have them but I think they have some kind of soft washer under the top nut. My Öhlins R&T fork has neither.
Next up is the rebound modification, where you´ll need to make up a new cartridge rod. The material you need is a piece of hydraulic pipe 10 mm by 6 mm (i.e., 2 mm wall thickness) in diameter. The thread at both ends is M10x1 mm.
Take the stock rod and measure the length from the top down to the cartridge holder. The stock holder is screwed inside the rod, the K-tech assy needs an outside M10x1 mm thread, so add 10 mm to the rod lengt and make the rod accordingly; thread at both ends is M10x1. Stock Showa rod and rebound shim stack on the left, new rod and K-tech shim stack on the right. Stock Showa cartridge rod with rebound shim stack holder disassembled. Note internal thread in the stock rod, as compared with the K-Tech rod with external thread.
When cutting the threads, the rod can compress slightly; to avoid problems getting the rebound needle in, clean out the tube at both ends with a 6mm drill bit, put nice chamfers where applicable, and clean everything up. I never bother to put back the hydraulic stops, so this saves a bit of job since you won´t have to make the grooves for the lock rings in the rod.
If the hydraulic tubing is zinc plated, you might want to take away the plating in the area passing through the bushing at the cartridge top; it might be a little tight otherwise.
Now assemble the complete K-tech rebound stack holder with shims and all on the rod, using a small drop of LocTite on the threads and a 3-jaw chuck or similiar to hold the rod, and tighten "properly".
Before putting everything back into the cartridge, make sure the cartridge tube is free from burrs and similiar after the drill-out operation. I use a reamer I happen to have for this.
Next is an extra; on one or two forks I´ve worked on the compression stack holder had moved on the lock ring, making it look pretty ugly and like it could work loose eventually. The lock ring is only 1 mm diameter wire, and a little heavier gauge lock ring would do niceley here. It took a while before I found it, but the piston pin circlips for 20 mm piston pins from JE are about 1.27 mm in diameter (probably some obscure inch dimension, like 0.05"). Part number is 787-050-MW, or at least that´s waht it says on the plastic bag, and it will fit perfectly in the cartridge groove.
However, the lower end of the compression stack holder won´t go through now, so you´ll need to slightly reduce the lower diameter to suit. If you do this, the whole setup will be much sturdier. On full extension, this lock ring holds the whole fork leg from falling apart, so I like the feeling of knowing it´s a bit more robust. If you don´t feel like going through this extra work, just skip it, and quit doing wheelies.
Now you´re ready to start assembling everything. Lubricate the rebound piston seal ring and rod, and push up through the cartridge. Screw the compression adjuster screw into the bottom of the compression stack holder, lubricate and carefully knock it in far enought to enable you to assemble the locking ring in its groove (you have to screw out the adjuster screw to do this), screw in the fork bottom screw again and carefully pull the stack holer back out until it bottoms on the lock ring.
Now is the time to measure cartridge stroke again and compare with a) cartridge stroke as measured earlier, and b) the fork stroke as per above. a) will be smaller than before, which is not bad, but should be bigger than b).
If it is not (as it was not on a Monster 900 - 2000 or so, late old-frame model, that I did recently), this is bad and has to be compensated for: Take everything apart again and start figuring where you could take away enough metal to create enough cartridge stroke to exceed b). So far, only this Monster 900 has been like that.
Next, put the cartridge back into the fork (with the bottom locating washer / cartridge seat), put a new copper seal ring on the bottom screw, put some thread lubricating compound on the thread (do NOT use LocTite), and tighten in a few steps to 35 Nm.
When you use a K-tech kit you do not need to manufacture any needles; you use the stock compression neede set-up, and the rebound needle comes with the kit (the pieces in the bag in the picture). Now take this needle with the spring, lubricate and push it down the cartridge rod until it bottoms out.
Next, take a 4mm diameter aluminium rod and push it down the tube and put some pressure on it to compress the spring. Make a mark on the alu rod at the top of the cartridge rod, pull it out and measure the length.
Then take the fork top nut, screw the adjuster screw all the way OUT, then screw it in again,counting the clicks until you run out of clicks; screw it back a little until you have distinct clicks again and note how many clicks you have.
You might have to do this a couple of times in order to make sure you´ve got it right. You will probably end up at around 35, and you´ll need them all. Screw the adjuster in these approx 35 clicks, and measure the distance from the bottom surface of the top nut up to the tip of the brass adjuster screw. Use this dimension, and the length of the cartridge rod above the lock nut as measured at the beginning,and the dimension of the alu rod as measured previuosly, to calculate the length of the alu maneuvering rod. It should be done carefully so that you get close; minor adjustments can be done by screwing the lock nut up or down slightly on the cartridge rod.
When you have the alu rod finished, drop it down into the cartridge rod.
Next, pour in some fork oil, either Öhlins R&T fork oil, or some 5W oil, and start working the cartridge up and down to get oil into the cartridge. Keep your finger on the alu rod to keep everything where it belongs. Pour in more oil, work the cartridge rod, and start measuring oil level. I usually start at 120 mm from the fork tube top with the fork fully compressed; you might have othere preferences. Keep it reasonable, a few mm this way or that might matter to Casey Stoner, but certainly not for me and for you, you have to decide.
When the oil level is done, drop in the spring, spacer and associated hardware, and lock the spring under the lock nut with the grooved spacer described before. Take the fork top nut, screw in the adjuster the 35 or so clicks you arrived at earlier, and gently screw down the top nut on the cartridge rod until the brass adjuster screw bottoms out on the alu rod inside the cartridge rod.
This should happen with the top nut reasonably close to the lock nut; if not, the alu rod is either too long or too short. With the top nut in this position, turn the lock nut gently against the top nut, screw out the adjuster a couple of clicks, and tighten the lock nut against the top nut. Remove the grooved spacer, make sure the spring spacer etc. are correctly positioned, and screw down the top nut.
Put the fork tubes back in the triples, tighten the lower clamp bolts to 15 Nm, tighten the top nut, and last tighten top triple to 15 Nm.
Next test the rebound damping: Spring preload fully out, compression damping fully out, rebound adjuster fully out. Pull the brake lever and push down as hard as you can on the forks and let go. On rebound, the forks should lightly top out and sink back a little bit. Screw down the adjusters one or two clicks at the time until this happens; my guess is somewhere between 5 and 10 clicks in.
Then set the compression adjusters 10 or so clicks out, put a tie-wrap around one of the forks legs (I prefer the right leg for convenience with the bike on the side stand), and push it up against the outer fork leg; you use this to evaluate spring preload and compression damping settings later.
Set the sag to some sensible value, don your riding gear and take a ride, enjoying your immensely improved front suspension. Play with the adjusters until you think it feels right when going over bumps, braking (tie-wrap!) or whatever you think is important. I always approach suspension settings from the soft side on all adjusters, working up to what I feel is right. This will take some time, but is well worth the effort; this whole modification is wasted if you don´t.
This might sound like a lot of work, and that´s because it is. However, if you plan on taking your forks apart for any reason, like a seal change, it´s not really that much more work. If you plan on doing a re-valve job anyway, only the manufacture of the rod, alu rod, and hollow allen screw is extra. You will have much improved suspension, and effective adjusters.
You can also revel in the fact that you now have made a moderately expensive performance conversion that actually works but is invisible, as opposed to a lot of carbon fibre and such which is moderately to very expensive, very visible but makes no performance difference whatsoever :-) Well, in most cases anyway.
There is also the risk this mod will incur further cost; you´ll probably want an Öhlins shock absorber as well pretty soon!