Shock Swap with 99-02 R6

[Fangfactor]

I agree chevaliernoir the spring is 2 stage and not progresive
With this set up the soft stage is around 35mm travel and taken up with rider sag.
I have only just fitted this setup and I take your point on variable rebound. This could be an issue at full lean on rough corners which could be unsettling with the potential to kick out.
Linear rate is definitely the better option. I am just trying this to gauge spring rate for my weight (100kg) as I keep reading that the R6 setup is a great improvement for fast road and occasional track but dedicated track needs a better shock. So reading between the lines I maybe thought a stiffer spring may make it a more suitable track option

Thank you for enlightening me to this potential situation, its much appreciated.

Ill go for a few more rides and gauge the feedback it gives in this situation.

 

[Fangfactor]

Thank you very much for your experience sharing.
I really like the idea in the principle, but I just have few comments :

The standard RC spring of not really "progressive". It has a certain rate for first centimeters of travel, then suddenly double the rate for the rest of the travel.
I think this , could be a good compromise for road usage, and for example in order to adapt to a passenger presence or not. But not for track or performance.

The main issue I see is about reboud influence. The rebound (and not the compression) is directly linked with the spring rate, as the role is to damp the movement due to the spring pushing the wheel down. If the spring rate is not consistent, you could not have a rebound consistent too, because it will be tune for the low or high spring rate, but will not follow the spring rate big change.

My comment is theoretical, and for sue real riding and real experience would be more valuable.

After taking consideration of your comments on the Rebound and rethinking it, the effect in the softer range should be theoretically slower due to the less load on the shock during rebound so therefore not a kicking sensation but the opposite. This would be a lot less of a worry when cornering.

I adjusted the rebound to click 7 from hardest (was 5) and tested on some quite rough sweeping corners.

I have to say it felt very planted and stable with no abnormal rebound sensations.

This setup for my weight feels just about right and I'm very happy with the outcome.

Thank you to all the R6 shock pioneers on this thread especially Formula390 for doing all the research and ground work for this mod

I will be using this set up at the next track day in conjunction with 20w oil in the forks and raising the oil level to racetechs recommended level of 130mm from the top (was 135mm) and see how it goes.

 

[Formula390]

I will be using this set up at the next track day in conjunction with 20w oil in the forks and raising the oil level to racetechs recommended level of 130mm from the top (was 135mm) and see how it goes.

I've only known one rider who ran 20w on the front, and the feedback I got was that it seemed too much. He was going to back down on the weight, but I didn't hear back what he went to or what his thoughts were. He is a fast racer, and was in the front pack and regularly on the podium... MY initial reaction when he told me he went from 4w (stock) to 20w was "REALLY???!" but his local suspension tuner thought that was the right setup for him. I don't like to second guess suspension guys who are right there with the rider and bike doing the track side rider support.... but in all honesty I thought 20w was... ... ... ... ...aggressive.

 

[Maddog Reynolds]

10w is similar to SAE 5, or maybe just a bit more viscous, as I remember it. I have some Motorex 10w fork oil to try, but I'm guessing it will be too heavy on compression damping, as the stock oil is already a bit harsh when cold, even though rebound is a bit soft for me.

I hope to fit better front units when I have time, but an R6 rear conversion comes first

 

[Fangfactor]

I've only known one rider who ran 20w on the front, and the feedback I got was that it seemed too much. He was going to back down on the weight, but I didn't hear back what he went to or what his thoughts were. He is a fast racer, and was in the front pack and regularly on the podium... MY initial reaction when he told me he went from 4w (stock) to 20w was "REALLY???!" but his local suspension tuner thought that was the right setup for him. I don't like to second guess suspension guys who are right there with the rider and bike doing the track side rider support.... but in all honesty I thought 20w was... ... ... ... ...aggressive.

Thanks for the feedback Formula390

After talking at the local shop about 20w they talked me out of it as they said the heavier oil will play havoc with cartridge type forks. especially on the small hits

But I must say though the 10w is working great for me

I suppose what Im chasing is more of the so called "'feeling'' in the front.

So Im thinking to get that there needs to be less floating and more pressure on the front tyre which is either more compression damping and/or stiffer springs.

Heavier oil should give more compression but also equally more rebound which I dont really want as rebound feels about right with 10w ( still thinking of trying 15w now just for the heck of it)

Do you think Heavier springs say 1.0 for my 100kg weight should be about right? I would probably stick with 10w oil as i really like the action it gives

Ive taken a couple videos of the shock and the forks while riding so I might have to figure out how you tube works and put up a link.

 

[Formula390]

Do you think Heavier springs say 1.0 for my 100kg weight should be about right? I would probably stick with 10w oil as i really like the action it gives

Sounds like stepping up to 1.1kg springs is your next step to me, and maybe 12w oil. Don't jump SO much with viscosity at one go. I try and not go more than 2w difference at a shot. Our weight is the same, and I'm running 1.1 springs and 9w oil, but the test mule here only sees canyon roads, and dyno pulls. LOL It's not living a life on the track tho, so higher oil viscosity isn't beyond reason. Try and not make more than one change at a time. .. If possible.

 

[Fangfactor]

Sounds like stepping up to 1.1kg springs is your next step to me, and maybe 12w oil. Don't jump SO much with viscosity at one go. I try and not go more than 2w difference at a shot. Our weight is the same, and I'm running 1.1 springs and 9w oil, but the test mule here only sees canyon roads, and dyno pulls. LOL It's not living a life on the track tho, so higher oil viscosity isn't beyond reason. Try and not make more than one change at a time. .. If possible.

Thanks again for your advice Formula390

Here a youtube clip of my current suspension mods in action with tyga twin pipe with db killer soundtrack

https://youtu.be/cCnGVPPaPF0

 

[CDN Duke]

Quick note to advise that R6 shock won't fit with T-Rex lowering link and Competition Werkes exhaust. Not enough clearance for the piggy back reservoir

I'm going to try the Triumph Speed 4 rear shock that has external reservoir as recently highlighted by German member on the Duke forum...

 

[DeathFromAbove]

So it looks like Suzuki part number 62684-40A10 is 10x17x30

I'll order one to try it out on the lower mount.

For the spring I'll be using an Eibach 2.25 inner diameter 7 inch free length 650lb/in (11.6kg/m) (part number: 0700.225.0650)
170lbs in gear.

 

[DeathFromAbove]

I can confirm that the Suzuki part is a perfect fit.

 

[CDN Duke]

I'm going to try the Triumph Speed 4 rear shock that has external reservoir as recently highlighted by German member on the Duke forum...

This wasn't going to be straightforward either so I abandoned that. It's for sale if anyone interested... http://www.kijiji.ca/v-motorcycle-p...06-triumph-speed-four-4-rear-shock/1260421261

I decided to go new and ordered a YSS shock instead.

 

[CDN Duke]

So it looks like Suzuki part number 62684-40A10 is 10x17x30

I can confirm that the Suzuki part is a perfect fit.

That's excellent info DFA, a great alternative at only $8 compared to the $20 for two reduction bushings and washers from Formula390.

 

[Diploman]

Personally, I think we should be happy to give Matt a little business in appreciation for the time and effort he put into developing this excellent, cost-effective shock upgrade. He magnanimously shared it free of cost with the 390 community, a valuable public service for which he deserves credit and thanks. If he makes a few bucks machining bushings and spacers, so much the better - he earned it.

 

[psych0hans]

Personally, I think we should be happy to give Matt a little business in appreciation for the time and effort he put into developing this excellent, cost-effective shock upgrade. He magnanimously shared it free of cost with the 390 community, a valuable public service for which he deserves credit and thanks. If he makes a few bucks machining bushings and spacers, so much the better - he earned it.

I second that...

 

[jjtard]

I third that....he was more than helpful with mine!!!

 

[sanchorc]

Hello has anybody tried swapping the R6 shocks on the ktm 390s? What is the whole process? And what components are required to perform the swap? Has anybody tried using the stock KTM springs with the R6 core?

 

[m3hl]

Hello has anybody tried swapping the R6 shocks on the ktm 390s? What is the whole process? And what components are required to perform the swap? Has anybody tried using the stock KTM springs with the R6 core?

Start reading on page 1

Formula390 has the kit (which I bought) or you can source the parts yourself.

 

[Lankho09]

First post on the forums. Last year while looking at big allroad bikes I stumbled across a Husqvarna 401 Vitpilen, a small naked based on the 390, sharing the frame and engine...well, sharing everything except the fairings basically. It's a completely useless bike. It won't take luggage, hell, it won't even take the OEM toolkit under the seat, no room! Being a naked, forget about any wind protection, making highways not terrible, but not enjoyable. A girl tried sitting behind me and right there and then decided she wouldn't ride pillion with me, so that's out. So I've got no other option than riding single on windy roads, and it's an absolute blast! The light weight and responsiveness of the small engine is great fun throwing around in the twisty bits!

However, even during the test ride I noticed something you already knew. The pogo stick that KTM/Husqvarna fitted on this bike does not deserve to be called a motorcycle rear shock. Now being a test ride, I wasn't really pushing it. Hell, even at the time of writing, I'm nowhere near the limits. And it's hard to pinpoint what I didn't like about the shock...it felt like it was to easy to go through the stroke, then bouncing back out without any dampening?

Someone on a local forum tried the R6 swap but said it wouldn't fit on newer years. I would like to make a hopefully useful contribution or share my project/experience, maybe someone more knowledgeable can run with it and perfect it further, or shoot it down and prevent me from catastrophic failure!

 

[Lankho09]

So, there's been a great deal of information on the swap of 2nd Gen R6 shocks onto 390's in this community and it all seems to have started with @Formula390's input. This whole thread has been nothing but informative for which I'd like to thank all of you. Since Formula390 started this swap thread with the intention of giving back to the community and I've learned basically all I know from this thread, it seems only fair to propose an alternative with the same intentions; giving back to a community.

With that in mind, please respect the following disclaimers; English is not my first language and I am in no way a suspension tuner. I've got a fairly basic grasp of suspensions but please consult a proper specialist or do your own homework before running with this, I'm open to critics or helpful suggestions.

Now that we've got that out of the way, lets get on to what could be an alternative to the R6 shock. I've heard reports of the R6 shock not fitting on newer models of the 390 and being the owner of a Husqvarna 401 '19 (Basically a KTM 390, sharing the frame and engine, only better looking!) I simply assumed that the R6 shock would not work on my bike. So, with that option ruled out, now what?

The R6 shock swap thread thought me the ideal length of the spring would be 305-310mm, slightly longer than the stock shock, giving a bit of added clearance to avoid dragging hard parts at lean angle and accomplishing a bit what one would get by sticking the forks through the clamps, geometry-wise, raising the rear a bit.

From there, I went searching for a) shocks at that length range and b) R1 2007 and R6 1999-2002 swaps. Why? Well, if the 2nd Gen R6 shock fits our bikes and I've seen the R1 2007 being mentioned as an alternative, reasonably, other bikes that fitted the R6 shocks as upgrades would have compatible rear shocks. The counter-argument could be that if the other bikes fitted the R6 shock as upgrades it would also stand to reason that their shocks would also lack in some way. But, we can't have it all with a budget, right?

Anyway somewhere along that process I stumbled along Ducati ST4 owners swapping shocks from Ducati 916's and several of the Monster series, apparently all shocks with an eye-to-eye of 305mm. Both of the shock clevises are eyes instead of a fork, and while the 916 series shock has a piggyback reservoir as part of the shock body, the ST4 appeared to use a remote reservoir. Well, with a remote reservoir, this shock could fit anything, either with stock or aftermarket exhaust!

Without doing much other research, I went onto the local Ebay alternative and found a Ducati ST4 shock for a few tenths. After having a few beers and a f*ck-it moment, I was now the proud owner of a Ducati ST4 shock, knowing pretty much nothing about it except it is supposed to be 305 mm eye to eye in length.

Upon arrival, I was well pleased. Sure, there was a lot of road grime, but having read the R6 thread, the bottom-out-bumper looked brand-new after some cleaning, the chroming on the damper rod has some very minor scratching though that appears more pronounced on the polished surface, it is neglectable for now, no pitting. Overall, really pleased.

Intending to tear it apart anyway and see what's what, let's get to the fitting part first. Below, some measurments of my own with a vernier caliper that's presumably slightly off (I've had a noticeable amount of readings ending in x.8, so I've went ahead and round it off to the nearest number) and some measurements of the all-knowing internet.

Husqvarna 401 2019;

Room between the singarm flanges (not including the raised boss of the mounting points!); 35mm
Width of the upper mounting flanges; 35mm
Width of the upper shock eye; 32 mm
Width of the lower shock eye; 32 mm.
Upper eye/bolt ID; 10 mm
Lower eye/bolt ID 10 mm

Ducati ST4 shock, exact year unknown;

Width of the upper shock eye; 23 mm
Width of lower shock eye; 23 mm
Width of the rebound adjuster casing; 36 mm
Nitrogen pressure (Racetech.com); 165 psi
Rear sag (Racetech.com); 35 mm
Stock Shock Spring Rate (Racetech.com); 9.8 kg/mm


Some random internet values;

ST2 & ST4;
305mm length

748 & 996;
305 mm length, 71mm stroke.

749;
305 mm length, 71mm stroke.

Monster 1000 '03-'05 & S4RS;
305mm length.

Ohlins STX 46 DU321 fitting;
M800 '03-'05
M996 S4R '03-'05
M1000 '03-'05
M620 '01-'05
M659 '06-'08
M750 '01-'02
M800 '05-'09
M900 '01-'02
S2R1000 '05-'09
S2R800 '05-'08
S4 916 '00-'05

Length 305mm, 66mm stroke.

Honda NC700/CBR600F
305 mm length.

Honda RS125 '99-'00
310mm length.

Honda CBR900RR '98-'99
305mm length.

Kawasaki 900R Ninja;
310mm length.

R6 '99-'02;
Length 305mm.
Width of both upper and lower eyes; 30mm
Lower bearing race; 17 OD x 12 ID X 30 W
Nitrogen pressure (Racetech.com); 165 psi
Rear sag (Racetech.com); 35 mm
Stock Shock Spring Rate (Racetech.com); 9.3 kg/mm


Great, so that was my notebook with the numbers out of the way. Let's get going and see if this was just a fucked idea or actually has some merit.

 

[Lankho09]

Other than this minor flaw, it seems to fit. Obviously the rebound adjuster is hitting on the swingarm flanges. The only way fitting it was placing some M8 rod through the swingarm flanges allowing for a slight 2 mm off-set fitment. Still, well pleased, the upper eye seemed fine and no part of the shock that is interfering is holding any oil or gas pressure so this may still be do-able for anyone with simple handtools! The banjo fitting of the ST4 shock body to the remote reservoir seemed fine to me, I fail to see how that could be an issue for interference for anyone otherwise considering the R6 swap.







Knowing the R6 and the ST4 have a 0.5kg/mm difference in stock spring strength and keeping in mind the stock R6 spring might often work for lighter riders during the swap to the 390, I'm not too worried. The original 390 progressive spring has a wider range to contend with!

So, still making broad assumptions, let's tear this shock apart, see what's what, file down the rebound adjuster and get on with it! The Racetech instructions may be helpful with this process.

https://racetech.com/page/title/IP Sk Rebuild STD

So, without these instructions I went ahead and built a spring compressor from 6x30mm flat bar steel and M10 threaded rod. BE ADVISED: PLEASE CONSULT YOUR LOCAL SHOP OR SUSPENSION TUNER!

Notice the 6x30mm flat bar steel is buckling in some places, I've drilled the holes 10,5 to allow for some angling of the steel to the shock spring. However, the use of the threaded rods to compress the spring damaged the threads sometimes. After the third time of use, I failed to notice the nut AND thread started turning instead of just the nut. When relieving the pressure because the spring had buckled in a strange angle, I've failed to notice the bars sticking to the threaded rod. In effect, the nut I was holding back turned out of the rod, jumping across the room, releasing all tension on the "spring compressor". The pieces of flat bar steel I didn't care enough for to smooth the edges jumped open and turned up- and outwards. At the time of writing, I've only found the washer which bounced of the cat tunnel. Yes, I've got a cat and I'm very happy she wasn't walking around during this moment of stupidity, I'm guessing a M10 nut pressurized by a 9.8kg/mm spring wouldn't have been benificial to my pets health. It would probably have an adverse affect on my knees too, which were close as well. Enjoy tinkering with your motorcycle, please don't be a Darwin award, get the proper tools or use a local shop.



Well, I managed to get the spring off, complicated by the fact the original shock collar added approx. 10-15mm preload and I didn't manage to turn the preload collar during the original fitment, it was just stuck.

Anyway, during this process I severly lacked in shooting pictures but most of the process speaks for itself. Otherwise the Racetech instructions should help or google rebuilding Showa Ducati ST4. (The remote reservoir shock unit is apparently a 46 mm Showa shock unit.)

RELEASE THE NITROGEN PRESSURE!

I've drilled the dust cap pressed in place on the ST4 shock. Be careful with the pressure, the dustcap is ca. 1 mm thick, a mm below that is the schrader valve and it's cap. For me, I've drilled the cap and then some of the schrader valve cap. Afterwards I stuck a screwdriver or any other tool in and pried the cap out. Beneath that there is the actual seal head with the nitrogen bladder. Great news, unlike WP shocks, it's a seal head with an actual schrader valve even with a nice cap. I've drilled through the dust cap into the actual cap on the valve but I wasn't intending on re-using this part anyway. You may also elect on drilling off-centre.

Removed the spring by compressing the spring enough to remove the lower collar beneath the spring. It has a slot in it allowing it to slip out when the spring is compressed enough. It has to go around the chromed part of the rod, it will struggle around the jam nut holding the lower clevis. (AGAIN; PLEASE HEED THE CAUTION, THIS IS NOT THE PROPER OR SAFE WAY TO GET THE SPRING OFF! GO TO A SHOP EQUIPPED TO DEAL WITH SPRINGS.)

Great, so now the nitrogen pressure is off and the spring is removed. Being a remote reservoir, I've removed the line between the reservoir and the shock body. Now, both the bladder side and compression adjuster side of the reservoir should be able to be easily pressed down and their respective circlips removed allowing to slide out either side.



Note, trying to move the lower clevis into the shock body may give you an indication on the binding of the seals and damping rod. Not being a suspension expert, I came to the conclusion that everything moved as I expected thus it would be alright. Without any pressure trapped inside, it al moved smoothly without any binding so I went ahead...

So, this leaves us to get the damper rod and valving body out of the shock body. Tap the end cap with a chisel/screwdriver/punch-trouch of your choice. this wil get the cap lifted, although crooked. So work at the edges available to you and try to get it out as straight as possible. Below it, you'll find the actual seal head, held back by a circlip ring.

After working out the circlip ring and a lot of pulling and wrestling, I gave up on just pulling out the actual seal head. I've greased the seal head and shock body with vaseline (petrolatum?) and started tapping on the lower end clevis, working my way around it.

So, so far, the bottom-out-bumper seemed to be in great shape and the chroming seemed to be very much alright, there was a fair scratch on the seal head though is was below the actual O-ring. Pretty certain it was already there but I may have caused it with the removal. Anyway, sanded it down with grit 400 and scotch brite and guessed it would be okay, not sealing anything really. So far, so good assuming this is a approximately 20 year old shock. Being in aviation maintenance I used mostly isopropylalcohol to clean components, pretty sure the average brake cleaner would accomplish the same thing with regards to road grime.

Anyway, I went for the clevis. Placing the damper rod (Gripping the nut on top of the damper rod that holds the valve stack, this nut is peened) in a vice and putting a 1/4" drive extension through the clevis the clevis threaded right off, leaving the jam nut in place at approx. two threads from the end of the threaded part of the rod. Looking at it, I decided the rod was threaded much more into the clevis then 1½ diameter of the shank and leaving it two threads more out would get me. approx 307mm height, smack in the middle of the quoted 305-310mm ideal shock length.

NOTE: After fitting the shock and a few more beers thinking about it, I realised, extending the clevis from the rod end also meant that the needle riding on the rebound adjuster was sitting lower by the same distance. In effect, yes, there is some ride height to be gained however, you're losing a big chunck if not all of the rebound adjustment. I've since reverted to the stock height value at the next fitting of the shock.