Showa Blues, part 1&2.

[MonsterHPD]

Hello,
I´m glad you find the tutorial instructive, or even inspirational :-)
Maybe it´s time for an update; I´ve done quite a few forks since this was written and I´ve gained some experience. There are quite a few alternative ways to upgrade the function of the basic 50/54 mm forks, some of which are:

•   Complete K-tech kit as per Showa Blues 1-2; this is best suited for track bikes since the ports are small, limiting flow.
•   Buy just the rebound piston holder / needle / spring / nut from K-tech, and use Racetech Gold valve compression pistons and shim set-up; this is better for the street, as are all the Showa stock pistons since both use big ports.
•   Transplant cartridge rod and compression pistons from some other Duc Showa fork (916/996/998/999); I think all Duc superbike forks after 888 have forks with proper damping circuit layout; 851 / 888 have the same rather useless setup as the 50/54 mm forks on Monsters etc. Or at least the few ones I´ve been into.
•   If you run clip-ons, the forks from 1000 SS are OK if you adapt the shim set-up (see Showa Blues Part 3). Or just use the relevant parts for your forks.
•   Transplant the cartridges from a Suzuki GSXR.

All these alternatives require various degrees of rework and fabrication and monetary input; none of them should be impossible with access to machine tools, some mechanical aptitude, time and patience.  
   
If I buy new springs, I use the 240 mm Öhlins springs, available in 0.5 N/mm steps frpm 7N/mm to 11 N/mm or so. To compensate for the shorter springs, I use 38 x 1.5 mm aluminium tubing in the bottom of the fork, plus the shim used for this purpose in most of the older Duc superbik forks.

The reamer is a 20 mm reamer, but since the holes needing de-burring are below the working area of the cartridge, I use a Dremel with a rather small wheel-type grinding tip and de-burr the holes, possible dress with some emery paper afterwards. The reamer is not really necessary unless you happen to have one handy.

I can put together a list of useful part numbers for those alternatives I´ve actually done myself, if you like.  

As for oils, I use 5W or 7 / 7.5W, mostly Motul; 5W for K-Tech (or Öhlins, almost identical), 7W for the others. I´ve not been systematic in my choice of oil brands which is not good; the 5W etc.  designations are not defined in any standard and actual viscosity can vary a lot for various xW oils from different brands.    

[teamamerica]

Thanks for the quick response.  I am new to all of the fork and suspension modification/rebuilding stuff. I had been reading on the other forum about modifications to the standard Marzocchi forks, I will leave those on the bike for now so that I can mess with the Showas, they are from a 900 SS and are 50/54mm.  I also need to wait for my clipons to arrive since the top of the forks protrude too far above the triple and end up interfering with the handle bar (I have a 2002 M620). 

I have access to some reamers but they are all fractional size, but that does not seem like a big deal to deburr, based on your comment.

I understand that there was a test in a UK magazine on the performance shocks that you had built. Sorry if I missed it but, can you advise where that I can possibly find a copy of that, I like reading about this stuff. 

Given there are so many combinations of modifications, what is the mod that you would suggest?  I will be doing this for a combination of street riding and track.  1)complete K-tech kit, 2)rebound piston holder / needle / spring / nut from K-tech, and use Racetech Gold valve compression pistons and shim set-up, 3) GSXR cartridge swap

Seems like if I get #1 and the Racetech Gold valves, I would have all the parts to do #2, correct?  I was initially going to just do the Gold valves until I stumbled on this thread explaining that there are still design issues with circuit design.

I don't mind spending some money on the parts, I just want to get the right stuff so I don't end up wasting money on stuff that I don't end up using. 

I can get a set of ohlins springs from a friend for $90, they are part number 8677-90 and I understand they were made for the 900SS.  He says the uncompressed spring length is 360mm.  I can't seem to find much other info on this spring, including the spring rate, would you happen to know?

The list of part numbers would be helpful. I'm sure I will have more questions as I start tearing into the forks.   
 

[MonsterHPD]

No problem with beeing new, this is no rocket science. It´s a good idea to do the Showas with no pressure to get them ready, always nice to be able to take things nice and easy.

I have the various Performance Bike articles as PDF´s; drop me a mail and I´ll mail them to you.   

What modification to recommend ... well, that depends. You need the rebound piston holders, and to my knowledge, K-Tech are the only people making them (apart from Showa, for all forks except the 50/54´s ...).
You could modify the stock holders and make your own needles etc; I have the drawings for that as well if you´d like to go that route, but it´s more bother than it´s worth. I only did them cause I found nothing else at the time.

I don´t think you´ll find the holders on K-techs on-line shop; you´d have to contact them. They have always been very friendly and helpful to me and expect nothing else if you contact them. The part numbers are as follows:

20K-MX006         FF REBOUND PISTON HOLDER SHOWA
20K-MX007A       FF REBOUND NEEDLE SHOWA
20K-REBSPRING   FF REBOUND NEEDLE SPRING
M6X1.00HN         FF PISTON ROD LOCK NUT M6x1.0

If you are mostly road and occasionally track, I´d say the big-port pistons (i.e., Showa stock, or Gold valves) are the better option. If nothing else, the big-port design leaves more room for shim set-up, and more room for comfort due to a higher flow capability.   

Gold valves or Showa stock is more or less a toss; hydraulically they are similiar and any differences are beyond the abilities of us mere mortals to detect.

I use the 240 mm Öhlins springs since they are an easy swap once you´ve done the initial installation. They will fit any 43 mm stanchion Showa (and probably any other 43 mm fork). Part numbers as follows:

4745-75, 7.5 N/mm (marking -75).
4745-80, 8.0 N/mm (marking -80).
4745-85, 8.5 N/mm (marking -85).
4745-90, 9.0 N/mm (marking -90).
4745-95, 9.5 N/mm (marking -95).
4745-10, 10.0 N/mm (marking -10)
4745-05, 10.5 N/mm (marking -05)
4745-11, 11.0 N/mm (marking -11)

As you can see, there´s a system to the designations, indicating the spring your friend has is a 9.0 N/mm spring. A stock SS spring is about 360 to 375 mm; I have some different notes and don´t know which one´s correct. I suppose a 9.0 N/mm spring could be OK for bare rider weights around 65 to 80 or so kilos; it´s a matter of much discussion and personal preference.

If there´s a need to compensate for shorter spring, the 996/998 (and maybe some others ...) have spring spacer tubes below the springs; and a spring seat washer ontop of the spacer; Ducati part numbers as follows:

Spacer: 349.1.099.1A
Washer / spring seat: 349.1.100.1A

I think the spacer is 75 mm long; there might be one 100 mm but I have no clear notes on this. If you need a longe tube, use alu tubing, 38 mm OD, and the washer on top of that. 

Finally, the GSXR (Showa) cartriges will fit with some work. They have 12 mm rods,as opposed to Ducati 10 mm, whis is considered an advantage since it provides more oil for the compression circuit to work with. They come in many different versions, and I don´t have much of a clue. The 2 sets I´ve bought are very different, but will both fit with some work. Might be a tutorial on that as well, one of these days 

Well,I think that´s it. Any questions; just let me know and I´ll do my best to answer.     
   

[teamamerica]

I tore apart my forks, the fluid was in great condition and pretty clean, I suppose the previous owner had replaced it regularly. it actually seemed redish and seems alot like Automatic Transmission Fluid. 

You  mentioned to measure how much the rod stick out from the top of the lock nut to the tip of the shaft with the orfice. I was careful to not back down the locknot from the top cap when I did so.  I measured 15.40 mm. 

I also re assembled the fork without the spring.  I did put back in the spacer tube, I don't think that affects the measurement right?.  The purpose of this is only to measure the maximum total stroke, right?  I measured a total stroke of 112.0mm from full compression to full extension.  I did this for both sides and I got basically the same. 

I have not yet removed the bottom screw since I only had a 19mm 1/2" drive socket and it won't fit.  I will borrow a 19mm 3/8" from a friend later today so I can finish taking that apart and measure without the cartridge.

[MonsterHPD]

The measurement of the cartridge rod above the lock nut is just to help define the length of the rebound adjuster rod.

The 112 mm travel as you measured is probably with the hydraulic stops still in place (the white plastic things on the cartridge rod)? I always throw them out, so you should repeat this measurement after you´ve taken them (and the lock rings on the cartridge) out. Compare this measurement with the stroke of the final assembled cartridge rod; if the fork stroke is smaller than the cartridge stroke you´re safe. Without the hydraulic stops, fork stroke should be close to 120 mm; if you use the K-tech parts with internal thread o the rod / external thread on the holder on a 50/54 mm fork, it should not be a problem.  

One note here: On a fork I did some time ago, after final assembly the rebound needle would not move freely. After quite a bit of fiddling around, I swapped the cartrigde rods for a different pair and the problem disappeard. It turned out that the thread in the cartridge rods were not centered well enough, and this caused the needles to bind. I´ve heard of one more case like this, so if it should happen to you, you know the problem most likely was caused by Showa, not you or K-tech.            

[teamamerica]

Yes this was with the hydraulic stops in place, when I did it the bottom adjuster screw was still torqued to the cartridge, therefore it was not possible for me to remove the hydraulic stops at that point.  I was just following the steps.  I will pull the stops and remeasure today. 

I think I will go with racetech valves.  I will order those this week.

I have a trip to next week with a 1 day stop over in AMS, I was thinking that perhaps it's easier and quicker to get the K tech parts there. I live in California so shipping the parts internationally may cost a bit, although I figure it should be quite light in weight since these are small parts.  I will call up the K tech people in the UK on Monday and find out.

[tendeep44]

hi my friend , verry impressive job!!! I am the owner of an harley XL 1200S with a showa fork, looks like verry similar to yours
i wan't to lower (about 2 inches) this fork.. you think i can put a spacer in the cartridge? or other thing to do? can you help me?
i send you a private message.
if someone have an idea..
thanks a lot

[babyonboard]

Hello!

Excellent thread even today @MonsterHPD

I had an issue with my Marjokis that one of the outer tubes was cracked and checked my options to upgrade a little bit my M695

So, guess what.. I have a pair of the shows blues bought in bargain I would say from an ST4s (tined version) and I ordered the K-tech kit. Now I am through the process to make the modifications.

Well is quite difficult for me to find and aluminum rod but easy to find a stainless one which i ordered. Of course, is more robust but i don't know if the weight will affect it. Also i don't have a lathe to put the o-ring on this and with the covid now is difficult also to find a store open for that so may possibly will not touch it for now, or if i find a 3 mm bolt (i have a 4 one) i will make the thread on the top cover. What is your suggestion on that?  Also note the cartridge rod length on my forks was measured to be 39.1mm total length.

Furthermore, i would like to ask if the picture of the compression stack of k-tech (the lower one) should be installed as per picture or vice versa? The shims should be at the bottom or the top of the stack? As it came the kit the bolt was facing the head on the shims so I am confused since I try to understand how they are working as well. so pls clarify on that if possible.

Also, i understand that for the compression stack I have to use the bolt supplied by K-tech and not the one used with the original valve

Thanks for your time spending. I will take some photos of the tools made for the diburing and other holders as a less professional option

[MonsterHPD]

Hi,
glad you enjoyed the thread, glad if it can be of help.
See answers below.


Well is quite difficult for me to find and aluminum rod but easy to find a stainless one which i ordered. Of course, is more robust but i don't know if the weight will affect it. Also i don't have a lathe to put the o-ring on this and with the covid now is difficult also to find a store open for that so may possibly will not touch it for now, or if i find a 3 mm bolt (i have a 4 one) i will make the thread on the top cover. What is your suggestion on that?  Also note the cartridge rod length on my forks was measured to be 39.1mm total length.

I don´t think it will make a difference function-wise due to weight, and I put the O-ring there as much to keep things from faling apart during handling s anything else. I also don´t thin you need to bother with the set screws in the top nut, the forks will function well also without them. 391 mm (presumably) seems OK.  

Furthermore, i would like to ask if the picture of the compression stack of k-tech (the lower one) should be installed as per picture or vice versa? The shims should be at the bottom or the top of the stack? As it came the kit the bolt was facing the head on the shims so I am confused since I try to understand how they are working as well. so pls clarify on that if possible.

The shims on the base valve piston go on the bottom, they are letting oil out of the cartridge when the fork is compressing. The check valve goes on top, letting oil back in when the forks extend.

Also, i understand that for the compression stack I have to use the bolt supplied by K-tech and not the one used with the original valve

That´s right. The stock screw is too short for the K-tech kit (or any other proper piston-and-shim set-up)

Thanks for your time spending. I will take some photos of the tools made for the diburing and other holders as a less professional option

Please do so. It´s always interesting to see new solutions

[babyonboard]

Hi Again .

Your response is impressive and I have to mention it !

Thanks for the info

Now one more question:

In the SKF seal pack, it came with a plastic washer. When I removed the seals from the fork the same had already a metal washer.
The seal from SKf ,was with smaller width from the installed one.

Should I use the plastic washer from SKF only, the existing metal washer or both of them. I will try to measure now but when installed only the plastic washer and the seal the space available at the bottom of the fork was only for the lock ring (you could see I mean the lock ring groove) . So now I am confused if I installed correctly the seals and if the plastic washer I left inside is ok or I should put back the existing metal washer

By the way even by air is working find the cartridge ( I checked and all valves are installed properly  )

[MonsterHPD]

Hello.

You should always use the metal washer; I install them with the flatter side towards the seal.The plastic washer is to compensate for the thinner SKF seal. Ioften find Thatcher with booth in place the snap ring won´t snap in, so I don`t use the plastic ring.

Use  a heat Gun to warm the slider area around the seal/Bush area, They Will go in/out much easier.

Hope tris comes out right, I hate the autocorrection on my nej IPad .....

[babyonboard]

Hi

Finally, I measured and installed the metal and the supplied plastic washer. They fit ok and snap ring installed also easily without problem

What I worry about is that I used medium adhesion locktite on the valves (just to keep you informed that I already installed the forks on the bike while I am in the process to overhaul an ohlins I bought,  while I replaced the fuel hose as well as proceed with several parts to be cleaned removed etc)

Of course not yet tested

Reverting

[MonsterHPD]

Hi,
I´m not quite sure what you mea with the Loctite comment. If it is of any heelp, I use a small dab of blue Loctite on the hollow screw for tha base valve, and a small dab of green (strong) Loctite on the rebound valve holder in the damper rod. Don´t use a big dab, I used too big a dab once and had to take it all apart since the needle got stuck.

[michael_chicago]

Great thread!

I've just installed the cartridges from an early 2000s Aprilia Mille into the adjustable forks of a 1993 900SS and thought I'd share the info that might be helpful.  I got a lot of info from Pajazo and dspear99pa's posts on the MS Ducati forum (and this thread, of course!)

I'm restoring an old racebike and got started on this journey when I discovered a broken plastic "hydraulic stop" in one of the legs.  I started researching online (what is this thing?).  Naturally, it's not available as a part and Ducati only sells it as part of the cartridge assembly.  Fortunately, the consensus seems to be that it isn't all that important and can be removed.  

However, during all this research, I found threads, like this one, about the "faulty" compression circuit in some of these early adjustable forks.  I've worked on Yamaha YZF750 Kayaba and the Aprilia Showa superbike forks and those both have the tube that goes into the damping rod with the needle controlling flow in the cartridge.  The Kayaba tube is not attached to the fork cap; the Aprilia is.

So, I was contemplating finding a set of the GSXR forks when I remembered that I had a spare set of the Aprilia Showa Superbike forks.  I've always thought these were the same as the 748/916/996 variety, though I've never compared internals.  The only difference I'm pretty certain on is that the Aprilia rebound screw is not indexed (the manual states "2.5 turns of adjustment," whereas the Ducati, the 996 manual I checked, anyway, states a certain number of clicks.  They could likely still be 2.5 turns irrespective of indexing.

The Aprilia forks were pretty beat up, and someone had sawed off the fender mounts (why???), so they were pretty much good for parts.  Here's the info that might be useful (taken with a tape measure, so probably not exact):

1.  The cartridge diameters, rod diameters and rod threads are the same.
2.  The cartridge length on the Aprilia is approximately 2.0" longer than the Ducati unit.
3.  Compressed length of both cartridge assemblies is the same.
4.  Extended length of Aprilia cartridge/rod is .4375" longer than the Ducati.
5.  The fork cap on the Aprilia superbike fork is a larger diameter (as you would expect).
6.  Fork cap parts are interchangeable, so I swapped the blue-anodized inner-part of the cap (with the adjuster screw and rod) into the 900SS cap.

Here you can see the two fork caps and the cartridges.  It's obvious the one from the Aprilia is longer:

IMG_E3636 by Michael Reed, on Flickr

I assembled the fork caps onto the dampening rods (indexing them so they had the correct range of adjustment).  So, the Aprilia at 2.5 turns and the Ducati at 14 clicks (how I interpreted it from the old manual; it's not that clear if the text refers to the compression or rebound adjustment).  Then I measured the distance from the base of the cartridge (with seat washer) to where the fork cap lip rests on the top of the fork leg:

900ss compressed:  22-1/8"
Aprilia compressed:  22-1/4"
900ss extended:  26-9/16"
Aprilia extended:  27.0"
900ss bottom of inside of fork to top of fork cap threads (compressed):  21-11/16"

So, the fork range movement won't be hindered by the new cartridge.

I assembled the Aprilia cartridge assembly into the Ducati forks, using all of the other Ducati internals, along with the modified fork cap.

IMG_3639 by Michael Reed, on Flickr

One glaring difference between the two forks is the compression adjuster.  The banjo-style bolt that threads into the rod is the same, but the adjuster that threads into the casting on the bottom of the fork lower is different.  The Aprilia fork has a small orifice between the casting and the inside the fork and the adjuster is a needle to control flow.

The Ducati adjuster, well, I'm not really sure how that works.  The threaded casting is open to the inside of the fork and the adjuster is obviously a different mechanism to control flow.  Somehow, I didn't try to turn the adjuster with the assembly out to try and figure it out.  But, I'm doing the 2nd fork today, so will investigate further.

IMG_3638 by Michael Reed, on Flickr

I'd be curious:  does anyone know how this adjuster works, and if there's any reason why this unit would not work with the "new" cartridge?

I assembled the fork and filled with Motul Expert 5W with an air gap of 130mm.  

I then tried the "bump" test with this fork compared to the other Ducati fork with the original internals.  Honestly, I couldn't tell much of a difference.  Worrying is that a couldn't tell a difference with either fork on compression with the comp adjustment backed all the way compared to turned all the way in.  Rebound damping seemed to work fine on both legs.

So, I'm wondering if everything is working as it should.  One thing I did notice during assembly.  When I assemble the YZF750 Kayaba fork, I always crank the compression adjustment in to slow the fall of the damping rod; it makes it so much easier to install the cap when compressing the spacer; I don't have to use wire or anything to hold the rod up because it falls so slowly.  I tried to do this with the 900ss forks with the Aprilia internals and noticed no change in the speed at which the rod fell no matter where the compression damping was set.  Normal for this fork?  I don't know.  It's been a long time since I did an Aprilia Showa fork, so I don't recall how those react.

I'm going to do the 2nd leg today, so will test the rate of fall on the Aprilia Showa fork when I disassemble.

One last thought:  The extended length of the modified 900ss fork is longer than the original; I didn't measure it, but it's probably the extra length of the Aprilia extended cartridge/rod assembly.  I can't imagine that would make too much of a difference. 

900 ss published travel:  120mm
Aprilia Mille pulished travel:  127mm

[michael_chicago]

I was staring at some of the parts on the bench today when I noticed that the dimples that hold the compression in the bottom of the original 900SS cartridge had been drilled out.  So, I pulled out the cartridge and discovered it was a Racetech Gold Valve.  I have no idea what the valving is.

I did the bump tests some more on the forks and I now feel like I notice more compression damping on the 900ss fork with the Aprilia internals.  This is testing back-to-back with the rebound valve on both forks completely open, testing compression circuit either fully open or closed.

Not sure if this is better or not, but it's definitely different.