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Author Topic: Showa Blues, part 1&2.  (Read 67184 times)
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« on: February 19, 2012, 08:12:59 AM »

Showa blues
or how to fix your Monster / ST / etc. front spring holders (part 1).

Update February 2018: Having learned a thing or two since this was first written, I will bit by bit update this to make it more up to date. Since these forks are no longer delivered (seems the forks on basic Ducatis are now even worse ...), maybe there is not that big demand for updated info, but since I have it ..... Updates will be posted in yellow.

Kind regards.

As they come, the stock Showa adjustable forks used on Monster 900´s, Monster 1000DS (but not the 1000DS Super Sport), ST2/4 etc. (for 50mm / 54 mm triples) are designed in a way that makes it impossible to really affect the compression damping.
It took quite a lot of figuring out by myself and a friend and fellow Duc-clubee to figure out what´s wrong with these forks, and work out a solution. By now I have modified quite a few forks utilizing various Öhlins and K-tech shim stack kits, all requiring significant modification to existing parts, and / or manufacture of new parts.

After having had contact with Chris Taylor at K-Tech, there seemed to be a possibility to modify the forks with minimal manufcturing of new parts necessary, using existing K-Tech hardware instead. Only the control rod for the rebound damping need to be fabricated. Access to some workshop equipment is still necessary, however.
Modified as described in the following, the Monster / ST style 50 mm / 54 mm forks will generally work as well as any cartridge forks, with maybe a slight focus towards track due to piston lay-out and shim set-up.  
Step 1: general disassembly.
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. Then take the fork legs off the bike.
Unscrew the top nut leg, push down the spring / spring preload tube assy and push a slotted washer under the lock nut to keep the spring / preload tube out of the way so you can get at the top nut and locking nut on the cartridge rod.

Fig. 1a by torbjörn bergström, on Flickr
Spring preload tube,  compressor tool (for the spring), slotted  spacer (for locking the spring pre-load tube below the lock nut), and top nut on top of the cartridge rod.

If you are unsure if you have a "bad" fork or not, compare the top nut with picture 8b.
If the rebound adjuster comes with a long rod attached to it, you have a fork with a "proper" daming circuit lay-out. In this case you will not have to do the mod described here.
Of the 50/54 forks, only the SS1000DS has the "good" rebound lay-out. However, both spring and damping is ridiculously soft. Changing to K-Tech parts can have benefits for track riding, but for the road updated shimming and proper springs will be the best alternative, $ for $. See Showa Blues Part3" for more info.  

Loosen the top nut and unscrew it completely from the rod, and measure how much of the rod sticks up above the locking nut. This dimension is handy to have as a reference, since it will affect the total available fork travel by a few mm. You also need it for determining the length of the rebound control rod; more on this later.
Take out the steel washer, plastic spacer, spring pre-load tube and spring, and lay them somewhere handy.

I recommend you then re-assemble the fork top nut back on the cartridge rod in roughly the position it will eventually sit when it´s all back on the bike, lightly lock it with the counter-nut on the rod, and 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 fork foot; it´s 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 in stock form. One leg is enough for this measurement.

Next, use an impact driver 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; some 1/2" sockets are too big.  I use a  3/8" drive socket with a 1/2"by 3/8" drive socket converter.

Fig. 1b Bottom plug removal by torbjörn bergström, on Flickr
Fig. 1b:
Bottom plug removal.

It may be possible without an impact wrench, but it has never worked for me.
Do the extended / compressed measurement routine once again on the bare cartridge; 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.
Both these measurements will be sort of base-line measurements, since the cartridge still has the hydraulic travel limiter in place. Removing it might / will change these measurements slightly.

Step 2: Compression stack removal.
Next, go to your drill press and drill out the dimples at the bottom of the cartridge to get the compression stack out.

Fig. 2a Cartridge dimple by torbjörn bergström, on Flickr
The dimple, and the one opposite, shall be drilled out.
The shiny thing is the compression stack holder.

Just drill through the cartrige wall and a little bit more, It does not matter if you drill al little into the compression stack holder, but don´t overdo it.

Screw the bottom nut a couple of turns back into the compression stack holder  and use a plastic mallet or similiar to tap  the compression stack holder (with stack ..)  far enough into the cartridge so that you can see the lock ring in the groove inside the cartridge tube.
Fig. 2b Comp Stack knock in by torbjörn bergström, on Flickr
Knock the bottom plug / compression stack holder into the cartridge

Prise the lock ring out; easiest done by pushing the ring opposite the opening down into the cartridge and then just lift by the ends out of the tube.  

Fig. 2c Lock ring removal by torbjörn bergström, on Flickr
Compression stack lock ring.

Getting the compression stack assy out of the cartridge can be tricky; for some reason the last bit always seem to be very tight.

Not wanting to use the cartridge rod to knock the compressions stack out, I used to use the bottom screw / compression adjuster screw and various suitable washers to pull the assy out of the cartridge by screwing the bottom screw into the stack holder against the washers on top of the cartridge until it bottoms in the holder, screwing it out again, add some washers, screw in again etc until you can pull the stack holder out. Now I have an old compression adjuster screw and a sliding hammer contraption to pull it out.

Fig. 2d Comp stack holder removal by torbjörn bergström, on Flickr
Fig. 2d:
Pull the compression stack holder out of the cartridge
When the stack holder assy comes out, the stack holder might look a bit second hand, but that´s not a problem.  

Step 3: Compression stack conversion:

To convert the compression stack from Showa to K-tech, you need to take the Showa scrapstack off the stack holder. You need a lathe or similiar 3-jaw chuck to hold the shim stack holder or you´ll run a serious risk to deform it, rendering it useless.

Fig. 3a Cooking LocTite by torbjörn bergström, on Flickr
Fig. 3a:
Use a hot-air gun to heat the stack holder to "sizzle hot" to fry the thread-lock
Take out the Showa stuff and throw it away. Or keep it if you like keeping trophies, or nail it to your garage wall. You could use it for target practise or something like that, it´s not very much more usefu for anything.
Take the K-Tech stack on its hollow Allen M6 bolt, add a small dab of blue Loctite or similiar to the thread and screw down into the stack holder. Note, a small dab since too much of this stuff will always end up where you don´t want it, like gluing your shim stack solid or do some other nice trick. Torque down to a reasonable feel; take care not to trap and deform the check valve shim.
 When you´ve got this done, the compression stack is finished.

 Fig. 3b Back Valve Check by torbjörn bergström, on Flickr
Fig. 3b:
This is the way the compression stack should look like when assembled.
You could also take the opportunity to check that the back-flow shim moves easily; this is where the oil goes to re-fill the cartridge on the return stroke.

Fig. 3c Comp Stack Comparo by torbjörn bergström, on Flickr
Fig. 3c:

Stock compression stack on top, K-tech version below.
Note the mangled lock-ring ridge on the top one, that´s how it came out of my forks the first time I took it apart.  

Step 4: Rebound stack conversion
You now need to get the rebound stack out; it´s at the end of the cartridge rod inside the cartridge. To get the rod out of the cartridge, first prise out the top lock ring above the white plastic cone on the rod, push off the cone (actually part of the hydraulic travel limiter assy), prise out the bottom lock ring as well and push the cartridge rod down out of the cartridge.  

Fig. 4a Hydrostop removal by torbjörn bergström, on Flickr
Fig. 4a:
This is the hydraulic travel stop; I throw them away. The 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 remove the stock shim stack holder from the damper rod, and replace with the K-tech part.

Start by drilling through the dimples in the rod that keeps the holder from turning in the rod.

Drill out the dimples.....

Heat the shim stack holder / rod end area with a hot-air gun until it is sizzling hot; this is (again) done to destroy the thread-lock agent put there by Showa. Failure to do any of these steps might lead to destroyed threads in the rod end, causing quite a bit of unnecessary work.

Fig 4c:
Just a some more hot air ...

Clamp the rod in a 3-jaw chuck or similiar and screw out the shim stack holder.
The rods I´ve done don´t have the internal thread all way down to the end, and after you´ve drilled out the dimples there likely will be some burrs that might cause the K-tech stack holder to cross-thread on the threads proper and end up mis-aligned with the rod.
Ideally, a 7.2 mm drill bit would clean this out without removing too much wall thickness. However, a 7.5 will do, but don´t feed any further than necessary since the K-tech holder has a shorter thread than the stock holder and you want to use all the thread you can. You could also machine off the bottom of the rod to get rid of the "bad" part

Fig. 4d:
Different rebound stack holders, r-to l: Stock; K-Tech for 10 mm cartridge rods; K-tech for 12 mm rods, and K-tech for 10 mm rods with external thread.  

For this conversion we´ll use #2 from the right.

Fig 4e:
Cartridge rod with stock rebound damping orifice still in place.....
.... and with the orifice removed and rod end cleaned up.

Before assembling the shim stack holder, you need to fix the top end of the cartridge rod: screw out the orifice, and clean out the end of the rod so it is reasonably smooth and burr-free.
After you have done all the modifications to the rod, clean it out with solvent and compressed air and make sure all the burrs and stuff is cleaned out.

Assemble the complete K-tech rebound stack holder with shims and all on the rod, again using a small drop of LocTite on the threads and a 3-jaw chuck or similiar to hold the rod, and tighten "properly".


Fig. 4f:
Stock rebound shim stack (top) and K-Tech
stack (bottom)

Before putting everything back into the cartridge, make sure the cartridge tube is free from burrs and similiar after the drill-out operation.
Edit Feb 2018: I now use a Dremel for this, before pulling out the comp assy, rounding all the holes inner edges to save the O-ring. I also do it before pulling the base balve out first time to save the O-ring. If you do this mod, you don´t need the O-ring, but since it´s an odd size, you never know ...

Fig. 4g:
Clean out any burrs before you push in the cartridge rod with rebound piston.

Step 5a: Lock ring up-grade.
This is an optional extra. if you don´t want to do this, just proceed to step 6.
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 (see the picture of the 2 compresion stack holder).

The stock 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 a suitable one, since next step is usually a 1.5 mm wire ring which is far too much.
However, eventually I found that JE piston pin rings were 1.27 mm diameter (probably 0.05"), and are available in 20 mm, and fit this purpose perfectly.
Part number is 787-050-MW, or at least that´s what it says on the plastic bag it comes in, and it will fit perfectly in the cartridge groove.
Please note, the lower end of the compression stack holder won´t go through now, so you´ll need to slightly reduce the lower diameter of the stack holder (about 0.10 mm or so) to suit. I put  the ring in the groove in the cartridge tube and measure, then test with the tube + ring, machining very small increments to arrive at a tight fit.

 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.  

Step 5b: Fork leg surface dressing.
This is another optional extra. If you have the lower fork leg separate, you could now dress the surface of the lower leg to get rid of any polished areas and get a nice criss-cross pattern. Use a  fine wet-grind paper maybe 1200 fine, some light oil as a cutting oil, and take care that the brake caliper hangers does not get your fingers.
Edit Nov. 2018: There are different views on what grit to use; I don´t know if there´s a "correct" grit. I now often use coarser than 1200, you´ll have to decide for yourself ...

Fig. 5b: You certainly need a lathe to do this
If you have the TiN-coated legs, DON´T do this.

Step 5c: Rebound oil leak sealing.
The final optional; since the stock cartridge rod is used in this conversion, the two holes that lead oil from the cartridge to the top nut rebound adjuster needle in stock configuration are still there, as are the holes in the top nut leaking the oil back into the fork leg (see picture).
You can use set-screws in the top nut,sealing these holes off. In this way, all the oil has to pass trough the compression andjuster and/ or shimstack on th ecompression stroke.
I´m not sure if it makes a noticeable difference or not. In theory it does, and it is not a whole lot of trouble so I usually do this.
Edit Nov. 2018: I now just do the O-ring on the control rod. Just make sure it´s above the entrance holes in the cartridge rod.  

Fig. 5c:
Leak holes in the top nut. The holes are about 3 mm in diameter. Get a 3.2 mm drill bit, cut an M4 thread,  and loc-tite M4 set screws in place.
You should be able to find them in any shop supplying screws and such. Again, buy something else at the same time, they are embarassingly cheap.  

Step 6: Cartridge re-assembly.
Now you´re ready to start assembling the forks. 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 the seal ring, and carefully tap the compression stack holder / shim stack assy into the cartridge tube far enought to enable you to assemble the locking ring in its groove, screw out the adjuster screw / assembly tool, assemble the ring, screw in the fork bottom screw again and carefully pull the compression stack holder back out until it bottoms squarely on the lock ring.
Edit Nov. 2018: Before you do this, it´s very important that all the holes in the cartridge have been de-burred / rounded, so the O-ring will not be damaged.

Now is the time to measure cartridge stroke again and compare with the cartridge stroke as measured in section 1. Assuming you have thrown the travel limiter away, when the cartridge bottoms out it will be the shim stack holders meeting, so be careful.

End of part 1.
« Last Edit: October 31, 2019, 01:07:42 PM by MonsterHPD » Logged

Monster 900-2002 (sold, alive and well in the UK), 749R / 1100 HYM combo for track days, wifes / my Monster Dark 800-2003 (not entirely "Dark" anymore and a personal favourite) , 50% of 900SSie -2000 track bike for rainy days-now with tuned ST2 motor and Microtec ECU. Also parked due to having been T-boned on track.
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« Reply #1 on: February 19, 2012, 08:57:07 AM »

nice writeup!

« Last Edit: February 27, 2012, 06:58:15 AM by ducatiz » Logged

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« Reply #2 on: February 19, 2012, 10:10:10 AM »

Showa blues
or how to fix your Monster / ST / etc. front spring holders (part 2).

Please go back to part 1 for the previous steps.

Step 7: Cartridge re-assembly into the fork.  
Put the cartridge back into the fork (with the bottom locating washer / cartridge seat in place),

Fig. 7a:
Don´t  forget to put the cartridge seat back on top of the cartridge before assembly in the fork.  

put a new copper seal ring on the bottom screw, put some thread lubricating compound on the thread (do NOT use LocTite, or you´ll never be able to disassemble this again), and tighten in a few steps to 35 Nm.

Step 8: Rebound adjuster modification.
This is an optional extra, but it is probably a more robust solution to machine the rebound "needle" off the brass adjuster screw in the top nut. I have done some with the needle left, and some with the needle machined off, don´t really know if it matters.
I´ve also seen a few different "needle" designs, so if you machne the tip off, the removed length might be a bit different depending on what needle you happen to have.

Fig. 8a:
To machine the adjuster, you obviously have to remove it from the top nut; just screw it out until it comes out.
After a while (about 35 clicks from full out) you will run out of clicks; just go on until you can push the needle out.Sometimes, the  little spring-backed ball responsible for the clicks will drop out, but surprisingly often it stays put.
If it does drop out, peek into the top nut from the bottom. Just above the last thread you´ll see a small hole. Put a dab of grease on a small screwdriver to hold the ball and carefully put it back in the small bore.


Fig. 8b:
Top nut (with spring pre-loader removed), "click" ball, adjuster screw with needle.
If you´d happen to lose the ball, don´t worry; you can get new ones at your bearing store. For some reason Showa has decided to use inch-sized balls, the ones I´ve checked were 1/8". If you do need them, buy something else at the same time; they are embarassingly cheap.

Fig. 8c:
Standard and machined adjuster screw. The tip is 8 mm long on this one.

Step 9: Rebound damping adjuster rod.
When you use a K-tech kit you do not need to manufacture any needles; you use the stock compression needle in the bottom plug, and the rebound needle comes with the kit. However, you have to manufacture an aluminium rod to control the rebound needle. To do this you must establish the proper length of this rod. Since the working space of the needle return spring is about 3 mm, you have to get this reasonably right, or you´ll miss the working range of the adjustment.

Take the needle with the spring, and drop it down the cartridge rod.

Fig. 9a:
This kit comes with this needle (no O-ring); it will drop right down the rod (or out of .... ).

Others I´ve seen come with an O-ring on the needle, this means you have to push the needle down the rod until it bottoms out.
Next, take a 5 mm diameter aluminium rod and push it down the tube and make a mark on the alu rod at the top of the cartridge rod. You want this to be to the closed position of the needle, so slightly press on the rod against the return spring of the needle until you can fell the needle stop against the seat.
Then, pull it out and measure the length.

Then take the fork top nut, back 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 I usually set it at 25-26 clicks.

Measure the distance from the bottom surface of the top nut up to the tip of the brass adjuster screw, this distance beeing "a".

Fig. 9b:
Measure the distance to the adjuster needle in top nut; this is the distance "a".

Next, measure the lenght of cartridge rod above the lock nut, distance "b".

Fig. 9c:
Measure the part of the rod above the lock nut; this is the distance "b".

By deducting "b" from "a" you´ll get the amount of control rod that shall protrude above the cartridge rod end in order to get a working rebound adjuster.

Fig. 9d:
This is about what it will look like if you have machined off the needle tip of the adjuster screw.

Edit 2013-01-25
The current .... SHO13 kit has a longer rebound needle than the one you see in the picture above:

Fig.9d: Some different K-Tech rebound needles. The current ...SHO13 kit needle is the one on top.

With the ... SHO13 kit needle, the adjuster rod will look like this (picture 9d1 and 9d2):

Fig. 9d1:
If you put the cartridge rod and adjuster rod along each other like this........

Fig. 9d2:
..... the adjuster rod should be appr. 41 mm shorter than the cartrige rod (still woth the brass needle tip machined off)

End edit 2013-1-25

Edit 2013-02-27:

Also, I´ve added an O-ring on the control rod:

Edit: O-ring 6x4x1 mm, groove dia 4.2 mm.
The groove is square in profile, to keep the O-ring in.

End Edit.  

Leave the needle tip and the control rod will be roughly flush with the cartridge rod.

You should do this pretty carefully so that you get close; minor adjustments can be done by screwing the lock nut up or down slightly on the cartridge rod.

To test if you´ve got it right, make sure the needle is still in the cartridge rod,  drop the control rod down on top of the needle, position the adjuster in the top nut in the screwed-in position used when taking the dimension "a" as mentioned above, i.e.8 to 10 clicks back from "no clicks".
Carefully screw the top nut down on the cartridge rod until the adjuster screw makes contact with the control rod; carefully screw it further down until the rebound needle bottoms and the nut won´t go down further.
In this position there should be some clearance between the bottom of the top nut and the lock nut. If not, your control rod is too short and you´ll have to make a new, slightly longer one.

Fig. 9e:
With the rebound adjuster in the "in" position (i.e., where the adjuster should be closed) and the needle seated against its seat (i.e., fully closed rebound adjuster), you should see some air between the top nut and lock nut
When you have this sorted, I recommend you lightly lock the top nut in place with the lock nut, screw down the top nut in the fork leg, and do the extended / compressed routine again, taking down the dimensions.  Presumably, the forks should bottom first, which in that case will now mean that the lower fork legs will bottom out against the bottom of the fork top nut.
Anyway, compare the fork stroke with the bare cartridge stroke; as long as the cartridge stroke is greater than the fork stroke, you are safe.
If not, go back, find the reason, compensate and proceed. Quickly said, but quite a lot of work, really.

Step 10: Fork re-assembly.
Next, screw off the top nut again,  pour in some fork oil, either Öhlins R&T fork oil, or 5W fork oil of any known brand, and start working the cartridge up and down to get oil into the cartridge. Using a hose with a couple of holes in it will help you catch the cartridge rod down in the fork leg, and keep the oil under slightly better control. There will be oil most everywhere anyway when you are finished, but in this case less is better.

Fig. 10a:
Work slowly, or you´ll have oil all over the place ....

In the end, you´ll probably have oil all over the place anyway, but trying to be neat helps.

If the oil will not enter the cartridge, you have probably put the shim stack on the compression stack holder up-side-down (been there, done that ...). Pour out the oil, disassemble the cartridge from the fork, dissasemble the compression stack and correct. Have fun.  

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 and no springs etc.; you might have other preferences. Keep it reasonable, a few mm this way or that might matter to Casey Stoner, but certainly not for me and probably not for you, but it´s your choice. If you decide on less air, make sure your forks will not lock due to oil overfill.

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.
Assemble the top nut as desribed in section 9, but after you´ve bottomed out the rebound needle, tighten the lock nut gently against the top nut, back off the adjuster a couple of clicks to protect the rebound needle, 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 in the top fork leg.

If you like, you could now do a "bump test": Screw both adjusters all the way out, and heave on the fork. It should pretty much pogo in and out with little resistance. Close the compression adjuster at the bottom of the leg and do the same; there should be a marked increase in resistance to compressing the forks. Now close the rebound, the return stroke should be real slow.  

Fig. 10b:Bump test.
If you make a handle like his one, you can  test various settings on your stock forks, and feel for any difference in compression or rebound damping.

On a standard fork, with the rebound damping even only slightly open, you will not feel very much difference at all in resistance when compressing the fork, no matter what the compression adjuster is set at.
Then do the same after you have modified your forks, and notice the difference: No matter where the rebound adjuster is set, there will be a noticeable difference in compression resistance with different settings of the compression adjuster.

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.

With everything in place, you can test the 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. This is a good starting setting for the rebound damping.
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 dust seal.You use this to evaluate spring preload and compression damping settings later after you have ridden the bike.

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 riding condition 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 take the hassle to get the settings well sorted for whatever riding you do.

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 alu rod is extra. You will have much improved suspension, and effective adjusters.
Just putting in a Racetech Gold Valve will not help (been there, done that ...), you have to do the modification to the rebound damping circuit to get an improvement.

Fig. 10c:
Racetech Gold Valve.Not much change, but it was before I knew ...
 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; when you realize how nice good suspension is, you´ll probably want an Öhlins shock absorber as well pretty soon!
Tools needed:
•   6 mm allen key or socket for the triple clamp bolts;
•   22 mm socket for the spring preload;
•   32 mm wrench for the top nut;
•   Spring compressor tool to compress the spring; not essential but very helpful;
•   Slotted washer to keep the spring down;
•   14 mm and 17 mm wrench for the top nut and the lock nut;
•   19 mm socket with small outside diameter for the bottom plug
•   Impact driver, also for the bottom plug,  
•   Piece of hose to help fishing up the cartridge rod when the spring, spring preload tube tec. are in place is very handy.

The modification outlined here is not the easiest and should not be attempted if you do not have the necessary skills and tools. I can´t say I had either when I started taking my forks apart, but in case of a screw-up I´d had no-one to blame but myself.
This how-to is written with the best intentions. Based on my own experiences and mistakes, it reflects the best of my knowledge, and I´ve tried to anticipate any problems you might encounter along the way accordingly. "Anticipate" in this case pretty much beeing an eufemism for "experiencing", actually, when I come to think about it.

However, I don´t expect it to be foolproof (you know how ingenious they can be ...), and you have to use your own judgement. If you do not feel up to the job, contact a reputable bike shop to do the job. If you do it yourself, you do it on your own responsibility, and if you screw up, it´s also on your own responsibility.  

I also have to mention I have not actually ridden a bike with a fork modified as per this description. I have, however, ridden bikes with similar K-Tech mods, only using slightly different parts, and I have two bikes (OK, one and a half) with the first version mod using parts produced locally and Öhlins shim kits. They have all worked very well. No guarantee, sure, but an indication, I believe. Also, the bump test indicated the same result as previous modifications; at least a further indication.

The K-tech parts used here are bits and pieces for various applications, the all-important rebound stack holder I think is for a "CR85/150 MX bike". I don´t know if that says something about Ducatis view of us Monster riders, sending suspension of this grade our way, but that´s what it is.

The parts needed are now available as a kit from K-Tech with the part number 20SSK-INT-SHO-13. Right now it contains the complete rebound stack with needle and spring, the complete compression stack with suitable, hollow M6 bolt. This means you have to use the stock compression stack holder.
Later, it will probably contain the the compression stack holder as well, so the kit will then be: rebound shim stack complete as a set on its holder with adjuster needle, and compression shim stack complete mounted on a new compression stack holder.
Edit: As far as I know, the kit does NOT include the compression valve holder.

You will then just have to:

• Dissasemble the cartridge;
• Throw out the compression stack with holder and substitute for the new part;
• Take out the stock rebound piston as outlined in section 4;
• Replace with the new rebound stack assy, also in in section 4;
• Manufacture a new control rod as per section 9;
• Assemble the whole caboodle as per section 6, 7, and 10.

Unfortunately, Showa has several different combinations of fork leg, cartridge, and cartridge rod lengths out there. Therefore complete kits with rods and everything cannot be supplied as a default solution. Some probably could already now; you´d have to check with K-Tech.

As the database grows, I´m sure more and more models will be added to a list of complete kits.
Presumably, you could also order complete kits from K-tech by taking your forks apart, take out the cartridge rod, measure from the top down to the rebound piston flange and inform K-tec0 If you do so, be careful to also state bike model and model year so that the database can be made more and more complete with time.

I´m sure, they can also do the whole mod for you if you send them your cartridges. This might be more or less practicable depending on where you live. Contact K-Tech at www.k-tech.uk.com for further details on parts and partners.
For those of you living in the US, there is a US disributor:

Orient Express
28 Grand Boulvard North
New York
+1(6312) 319 552

Legal aspects and disclaimer.   
Since we are very obviously dealing with safety-related parts and modifications here, and with the sue-for-money-if-you-can-or-even-if-you-really-couldn´t mentality rampant, I´m not sure if you can order the K-Tech parts yourself, or if you have to order them thru a dealer / retailer, or if you have to get the job done by a K-tech autorized bike shop. Check for a K-tech dealer close to you, and start the discussion with them.
I´m sure there are aspects of this job I have not thought about. If you set out to do this modification, you do it on your own responsibility and you have to use your own judgement and experience to make sure the job is done properly.
That said, if done properly I´m sure you will be very happy with the results.
« Last Edit: November 28, 2019, 02:09:28 PM by MonsterHPD » Logged

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« Reply #3 on: February 19, 2012, 08:27:18 PM »

Holy crap! Now I know why I pay guys like you to do this stuff for me!  bow down

Nice tutorial!

Mike in Tacoma
'08 S2r 1000 - Red on Red
'96 900 SS/SP
'02 ST4s (gone but not forgotten)

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« Reply #4 on: February 23, 2012, 01:29:44 PM »

Holy crap! Now I know why I pay guys like you to do this stuff for me!  bow down

Nice tutorial!

Thanks, glad you enjoyed it.
It was my intention to be thorough in order to make it simple for anyone wanting to improve on their front suspension without having to adapt some other forks.
I´m starting to wonder if I´ve scared people off instead ... Huh?

Anyway, it really is quite basic. Just let it take the time it takes, and nothing much can go wrong. It´s definitely worth the trouble and expense.

Monster 900-2002 (sold, alive and well in the UK), 749R / 1100 HYM combo for track days, wifes / my Monster Dark 800-2003 (not entirely "Dark" anymore and a personal favourite) , 50% of 900SSie -2000 track bike for rainy days-now with tuned ST2 motor and Microtec ECU. Also parked due to having been T-boned on track.
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« Reply #5 on: February 27, 2012, 06:45:27 AM »

I am really glad you are sharing your efforts to fellow ducatisti and respect your persistence in finding a solution for the problem with monster forks!

I am definitely going to do this mod on my ss900 forks!. I have once installed Bitubo valves to some S4R forks and wondered too why the compression adjuster doens't seem to have any effect. I never was really satisfied with the damping of the forks even after the mod.

However there is one thing that caught my attention on this mod.

If there is no O-ring on the rebound adjuster needle, won't the oil still be able to escape upwards through the damper rod? Even if you seal the holes at the fork cap, this leaves air in the upper part of the damper rod and this air would compress when the pressure inside the cartridge gets high during the compression stroke and let some oil escape from the cartridge. The amount of oil would be low but so is the amount of oil flow through the compression valve. Of course this escaped oil would return to the cartridge afterwards, but i suspect that completely sealing the lower end of the rod could give a more solid damping action.

So I would be interested if you can find out if the needle with the O-ring you had in the pictures from the previous instructions is compatible with this mod (if it would seal against the stock damper rod) and if you could also give us the part number for the o-ringed needle.

This is the pic of the needles I mean
« Last Edit: February 27, 2012, 06:52:48 AM by pajazo » Logged
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« Reply #6 on: February 27, 2012, 07:16:12 AM »

On a second thought, maybe the o-ring in the needle would not be so good idea. As the oil can flow freely through the body of the rebound valve during compression stroke, the full damping force is acting through the small area of the damping rod on the fluid inside the cartridge. This high pressure would cause an enormous force on the rebound needle if it was sealed against the damper rod (If the rod diameter is 10mm and the inside diameter 6mm, it would be 36% of the total compression damping force). This force might be enough to permanently deform the slim 5mm aluminum rod and cause the rebound needle to lose its setting. And it would transmit a considerable force to the threads on the stock rebound adjuster.

Another thing coming to my mind is that the weight of the 5mm rod will be resting on the small spring of the rebound needle. Is the spring stiff enough to keep the needle from banging against the rebound valve holder in sharper bumps? If not, I would probably try to attach the 5mm aluminum rod to the rebound adjuster at the fork cap. They could probably be quite easily joined by making threads to both.

Edit: Ok, I'm slowly starting to comprehend the whole workings of the forks. Even if there was an O-ring on the needle, the pressure would still be passed to the inside of the damper rod by the two small holes at the lower end and this pressure would then exert a force on the adjuster screw at the cap directly. So there is really no easy means to prevent this from happening. If there has been no damage to the rebound adjusters of any of the forks you have already modified, this is probably not an issue.

I would still be worried about the oil inside the cartridge having an escape route through the two holes at the lower end of the rod and then through the fork cap holes if you dont seal them and whether the needle spring will be stiff enough to support the aluminum rod in bigger bumps.
« Last Edit: February 27, 2012, 09:15:52 AM by pajazo » Logged
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« Reply #7 on: February 27, 2012, 01:52:40 PM »

your thinking is along the same lines as my own, and the kit me and my partner first made had the rod threaded to the needle at one end, and to the adjuster screw at the other end, and an O-ring to seal the whole thing (and provide som cusioning):

I´ve also been worried about the design using a "loose" needle to seal an orifice with very varying flow that would tend to blow/suck the needle up and down, possibly creating wear at the seat etc. I don´t  know if this could be a problem, but all the K-Tech kits are like that; I also believe the 888 forks were like that, for instance. The Duc 848 and 1000DS Supersport forks have "solid" needles so both systems are around.  I suppose only time can tell, but I believe K-tech and other would not do it this way if it were a problem.

I do not think that the weight of the alu rod is a problem, the hydraulic forces acting on the needle should be magnitudes bigger.
Sorry, got this a bit unclear: The hydraulic forces and the weight of the rod would act in the same direction when the needle / orifice is active (on the rebound stroke). I´ll see if I can get a view on this from K-tech.

From an engineering "neatness" viewpoint, I would prefer the "solid" adjuster / rod / needle combo, but then I´d be back att making all the parts myself. Lazyness, maybe  Undecided

Of course, there is room for improvement here, by making a rod that is threaded to the adjuster screw and has an O-ring groove somewhere just above the "access holes" in the cartridge rod.

Part reason for using the 5 mm rod inside the 6 mm inside of the cartridge rod is to create a very long and narrow path with a lot of friction for the damping oil, but sealing the holes will of course provide a positive seal.
When summer arrives here, I will ask the owner of the forks in the how-to to test first as is, then we´ll put in the sealing screws and see if that affects the settings.
Doing just the bump test as-is (fork caps holes open), there is a definite reaction to compression adjuster setting even with the rebound fully open. At least better than stock, but maybe not as good as it could be.....  

Well, 1 each "I think", "I suppose", "don´t know", and 2 "I believe"... not much in the way of clear answers here ... Embarrassed . Hope there´s some help in there at least to help your thinking along.        
« Last Edit: February 29, 2012, 09:42:28 AM by MonsterHPD » Logged

Monster 900-2002 (sold, alive and well in the UK), 749R / 1100 HYM combo for track days, wifes / my Monster Dark 800-2003 (not entirely "Dark" anymore and a personal favourite) , 50% of 900SSie -2000 track bike for rainy days-now with tuned ST2 motor and Microtec ECU. Also parked due to having been T-boned on track.
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« Reply #8 on: February 28, 2012, 06:01:13 PM »

thanks for getting all that down in one place.  Forks are the one area of my bike which really disappoints me.  Not very confidence inspiring in corners, harsh, /sigh.

When I can find someone to do this that won't crush my bank account, i'll let you know how it goes.

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« Reply #9 on: March 01, 2012, 07:07:56 AM »

A very simple solution to the design flaw of these forks would be closing the rebound adjuster completely and drilling a small hole through the rebound valve (or check valve shim) to compensate. Then there would be no leakage through the damper rod but we would lose the slow speed rebound adjustment. Getting the hole size right would likely require some experimenting.

Another possible mod coming to my mind would be to transplant upper caps and cartridges from srad 750 forks. The top triple clamp diameter is the same and the top cap thread looks similar and based on information I found on internet forums (very reliable Smiley the fork lenght is the same on both bikes (730mm) so it is possible that the cartridge length would be suitable too. As far as I know the gsx-r dont have a similar design flaw as the ducati forks. I'm not sure if the thread on the bottom of the cartridge is the same but swapping the compression stack holder would solve that.
I have ridden my brother's srad 750 and liked the forks even with stock valving.
« Last Edit: March 01, 2012, 07:16:35 AM by pajazo » Logged
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« Reply #10 on: March 01, 2012, 01:19:47 PM »

As you have concluded, there are many ways toimprove on the function of these forks; however any method that does not involve changeing shim stacks would leave you with the stock compression shim stack, which is not really a shim stack at all but rather a sort of blow-off valve. I have no idea how it would copw with suddenly having to handle the oil flow previously leaked out thru the rebound circuit. Also, the rebound shim stack is as far in in the fork as you can get, making change-and-test a very laborious proposition.

I´m sure there are other Showa forks on the market where the internals would transplant, and would be an improvement on the Monster Showas. If you find one,  let us know.   

Monster 900-2002 (sold, alive and well in the UK), 749R / 1100 HYM combo for track days, wifes / my Monster Dark 800-2003 (not entirely "Dark" anymore and a personal favourite) , 50% of 900SSie -2000 track bike for rainy days-now with tuned ST2 motor and Microtec ECU. Also parked due to having been T-boned on track.
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« Reply #11 on: March 01, 2012, 09:14:36 PM »

maybe I missed it...

does this part:

Get replaced by this part in the K-Tech kit?


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« Reply #12 on: March 02, 2012, 06:19:45 AM »

No, the first part is a needle fabricated for an earlier mod by monsterhpd. The second part is a k-tech needle that is one of the parts  used in this mod.

Monsterhpd: to get to the rebound valve and shims to drill the hole would require the forks to be completely taken apart, so if I would do that, I would of course also change the valving to something better. I only suggested it because it would not be necessary to make any diy parts.

I will probably see if I can find some cheap srad internals to try if they will fit. If I do, I'll report the results.
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« Reply #13 on: March 02, 2012, 11:18:35 AM »

No, the first part is a needle fabricated for an earlier mod by monsterhpd. The second part is a k-tech needle that is one of the parts  used in this mod.

Monsterhpd: to get to the rebound valve and shims to drill the hole would require the forks to be completely taken apart, so if I would do that, I would of course also change the valving to something better. I only suggested it because it would not be necessary to make any diy parts.

I will probably see if I can find some cheap srad internals to try if they will fit. If I do, I'll report the results.

Correct, two versions of the same part.

Send me a mail and I´ll give you a list of cartridge dimensions (very incomplete, but still ....).

BTW, maybe I missed that, but what is srad?  

I asked Chris at K-tech about the questions concerning the "loose" adjuster rod; they´ve been doing it like this for years with no known problems.
As mentioned, my Öhlins fork is also like this as are several others. I woul not expect it to be a problem.
« Last Edit: March 02, 2012, 11:36:44 AM by MonsterHPD » Logged

Monster 900-2002 (sold, alive and well in the UK), 749R / 1100 HYM combo for track days, wifes / my Monster Dark 800-2003 (not entirely "Dark" anymore and a personal favourite) , 50% of 900SSie -2000 track bike for rainy days-now with tuned ST2 motor and Microtec ECU. Also parked due to having been T-boned on track.
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« Reply #14 on: March 02, 2012, 06:04:07 PM »

Correct, two versions of the same part.

ok, that's what I thought.  thanks.


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