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Fitting Yss Valve Emulators


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#1 Norwegian

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Posted 09 May 2021 - 02:55 pm

So my YSS PD 360 fork valve emulators finally arrived from Simon at bikerevival.co.uk (£66 delivered). Got to work, armed with Carpe knowledge in general and support from Bjørge and Dandy Warhol in special (muchos gracias!).

 

Very straight forward job, couple of hours work barring mishaps or stuck bolts. I took a few pics, and also gleaned an understanding of the existing rebound adjustment that I haven't been able to find explained online. I'll elaborate on that in another post.

 

I put the rear on a paddock stand and suspended the front from the garage roof with simple ratchet straps hooked to the bar. 

Attached File  Bike suspended.jpg   130.85KB   0 downloads

 

I didn't have a 19 mm hex bit for the front wheel axle bolt, so I had to improvise one:

Attached File  Wheel bolt tool.jpg   143.96KB   0 downloads

 

Fork legs came off easily. First release the spring preload all the way, loosen upper pinch bolt, then loosen the caps a half turn, then loosen the lower pinch bolts. 

 

After taking off the caps with the rebound adjuster rods I drained the legs. Surprisingly, one had a light grayish gluelike substance in it, the other a very dirty dark oil. I know the fork gaskets was changed by the previous owner only a few thousand kms ago, so I really expected to find better oil than this. 

 

Bottom bolts spun out without protests with an impact driver. A fairly long 10 mm hex bit is needed. Another surprise - quite a bit of oil was left in the forks and obviously started leaking all over the place as soon as the bolts were out. 

 

The valves comes directly on top of the compression piston that is bolted to the bottom of the fork, and additional 8 mm holes must be drilled and deburred in the piston stem. I decided to keep the rebound rotary valve for now.I set the valve preload at two turns, and left the rotary valve at its smallest opening. I did not braze shut the rebound adjustment hole, nor did I enlarge the lower oil return hole (none of which are mentioned in the YSS instructions, but I have seen it in some Race Tech instructions, and the valves are pretty much the same).

 

Attached File  YSS valve placement.jpg   52.04KB   0 downloads

Attached File  YSS valve detail.jpg   72.91KB   0 downloads

 

The spacers have to be shortened in accordance with the extra height added by the valves. I have a small metal lathe that I convinced myself I could not live without owning years ago (turned out I was right), otherwise a hack saw would do it, too. I removed a couple of mm less than the the height of the valve, to give just a little more preload when assembled. Rear end is elevated 25 mm by means of shorter dog bones, so that is why I want a little bit more leeway in the front, too.

 

Attached File  One spacer cut.jpg   155.49KB   0 downloads

Attached File  Both spacers cut.jpg   165.56KB   0 downloads

 

 

The original rebound adjusting rod has to be cut. This is the point of no return to the original setup (the extra holes in the compression piston stem are easily covered with a sleeve if needed). 

Attached File  Rebound adjuster cut.jpg   108.92KB   0 downloads

 

For oil I went with ATF Dexron III, and put exactly 500 ml in each leg. 

 

Reassembly was straight forward and surprisingly devoid of nasty surprises. 

 

 

Then test ride! Did the bike transform completely, to a modern day superbike wonder, plush and firm at the same time??

 

Not really. It still dives on low speed sudden braking, and it is still somewhat hard over speed bumps at slightly higher-than-adviced speed (only for test purposes, mind you). Twisties at speed are just as fun as ever, and it tracks curves wonderfully and reliably. But then again, I wasn't unhappy with it before. I'll give it some time, and then perhaps fiddle a bit with the valve pretension, rotary valve and eventually oil weight.


Edited by Norwegian, 11 May 2021 - 11:33 am.

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#2 dandywarhol

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Posted 13 May 2021 - 09:05 am

Good job. I'm surprised there will be enough opening to enable the oil to get to the YSS valve if the rotary valve is left in place. The last set I did I removed most of the webbed area for the "D" rod but left a bit to enable a screwdriver to catch the rotary valve and revolve the valve for adjustable rebound facility. That now gives completely adjustable compression and rebound, albeit a bit fiddly.

 

Fitted a pair of YSS valves to my Kawasaki W800 keeping the fork legs in the yokes - that's a first for me  :badgerrock:  :pimp:


Edited by dandywarhol, 13 May 2021 - 09:07 am.

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#3 Norwegian

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Posted 13 May 2021 - 09:35 am

Agreed. I believe the rotary valve will restrict the oil flow too much at high speed compression. I will open it again and remove the webbing, and also turn it to the second lowest setting - at the lowest, rebound seem to be a tad overdamped.

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#4 Bjørge

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Posted 21 May 2021 - 01:33 pm

So my YSS PD 360 fork valve emulators finally arrived from Simon at bikerevival.co.uk (£66 delivered). Got to work, armed with Carpe knowledge in general and support from Bjørge and Dandy Warhol in special (muchos gracias!).

 

 

[...]

 

Then test ride! Did the bike transform completely, to a modern day superbike wonder, plush and firm at the same time??

 

Not really. It still dives on low speed sudden braking, and it is still somewhat hard over speed bumps at slightly higher-than-adviced speed (only for test purposes, mind you). Twisties at speed are just as fun as ever, and it tracks curves wonderfully and reliably. But then again, I wasn't unhappy with it before. I'll give it some time, and then perhaps fiddle a bit with the valve pretension, rotary valve and eventually oil weight.

 

I swapped to linear stiffer springs at the same time, this may explain your somewhat different experience. Also, dunno how old the fork oil was, I mean if it's old even changing oil could be a revelation.....


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#5 Kebab897

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Posted 08 June 2022 - 06:03 am

Good job. I'm surprised there will be enough opening to enable the oil to get to the YSS valve if the rotary valve is left in place. The last set I did I removed most of the webbed area for the "D" rod but left a bit to enable a screwdriver to catch the rotary valve and revolve the valve for adjustable rebound facility. That now gives completely adjustable compression and rebound, albeit a bit fiddly.

 

Fitted a pair of YSS valves to my Kawasaki W800 keeping the fork legs in the yokes - that's a first for me  :badgerrock:  :pimp:

This is a very helpful page as I'm currently converting my own 2008 forks with YSS emulators: I also bought a slightly bent pair of earlier (2002-03) forks as I intend to use their damper rods / fork caps.

 

Now I have them all apart, I noticed that not only are the springs different lengths, but setting the combined springs / spacers together side-by-side there is still a difference in length (didn't get a chance to measure last night but probably between 5 - 10mm). I thought spring/spacer was the only difference between the early and late versions of forks, could there be other differences? Sadly with the bent stanchions I can't measure overall height / fork length accurately.

 

Anyway, a few Qs:

  • Bottom of damper rods - best with six holes, 8mm in diameter?
  • YSS emu - seems to be preloaded out of the box - I take it that it's set to two turns, or should I set it my self? From dim recall, I thought the Race-Tech version was 2.5 turns of preload as opposed to two turns
  • Damper rod's 'D' area (or Radioactive symbol as I see it :)) - do I remove it all, or widen out the existing holes as much as possible?
  • Do I need to seal the existing damper rod holes or just keep them as they are?

Thanks



#6 dandywarhol

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Posted 08 June 2022 - 08:42 pm

This is a very helpful page as I'm currently converting my own 2008 forks with YSS emulators: I also bought a slightly bent pair of earlier (2002-03) forks as I intend to use their damper rods / fork caps.

 

Now I have them all apart, I noticed that not only are the springs different lengths, but setting the combined springs / spacers together side-by-side there is still a difference in length (didn't get a chance to measure last night but probably between 5 - 10mm). I thought spring/spacer was the only difference between the early and late versions of forks, could there be other differences? Sadly with the bent stanchions I can't measure overall height / fork length accurately.

 

Anyway, a few Qs:

  • Bottom of damper rods - best with six holes, 8mm in diameter?

Yes

  • YSS emu - seems to be preloaded out of the box - I take it that it's set to two turns, or should I set it my self? From dim recall, I thought the Race-Tech version was 2.5 turns of preload as opposed to two turns

You'll probably need a few attempts - try as standard first

  • Damper rod's 'D' area (or Radioactive symbol as I see it :)) - do I remove it all, or widen out the existing holes as much as possible?

I usually remove the complete rotary valve but the last set I modified I just made the area as big as possible to allow the oil up but retained some rebound adjustability

  • Do I need to seal the existing damper rod holes or just keep them as they are?

If you retain the rotary valve assembly then you don't need to seal up the holes around the top. From memory, I finally brazed the hole in the waisted part of the damper rod and redrilled a 2mm hole but to be honest, I've actually forgotten cos I tried so many different permutations..................  :hide:

There is a difference in spring and spacer size in later models

 

Thanks


Edited by dandywarhol, 08 June 2022 - 08:43 pm.

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#7 Norwegian

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Posted 09 June 2022 - 06:48 pm

Whe I fitted the YSSs I left the rotary valves intact, with seemingly no adverse effects (left them at smallest hole for good rebound damping). I also left the valve pretension at the factory setting, two turns, and used ATF oil. I am about 105 kilos fully geared, and the front still dives easily on braking. Rebound is good, though. So will tighten the valves a bit later, and possibly go for a heavier oil as well.

Edited by Norwegian, 09 June 2022 - 06:48 pm.

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#8 dandywarhol

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Posted 10 June 2022 - 01:15 pm

Whe I fitted the YSSs I left the rotary valves intact, with seemingly no adverse effects (left them at smallest hole for good rebound damping). I also left the valve pretension at the factory setting, two turns, and used ATF oil. I am about 105 kilos fully geared, and the front still dives easily on braking. Rebound is good, though. So will tighten the valves a bit later, and possibly go for a heavier oil as well.

 

That's interesting, I thought the rotary walve would affect the compression oil flow path - good one!


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#9 Kebab897

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Posted 15 August 2022 - 04:26 pm

 


 

Anyway, a few Qs:

  • Bottom of damper rods - best with six holes, 8mm in diameter?

Yes

  • YSS emu - seems to be preloaded out of the box - I take it that it's set to two turns, or should I set it my self? From dim recall, I thought the Race-Tech version was 2.5 turns of preload as opposed to two turns

You'll probably need a few attempts - try as standard first

  • Damper rod's 'D' area (or Radioactive symbol as I see it :)) - do I remove it all, or widen out the existing holes as much as possible?

I usually remove the complete rotary valve but the last set I modified I just made the area as big as possible to allow the oil up but retained some rebound adjustability

  • Do I need to seal the existing damper rod holes or just keep them as they are?

If you retain the rotary valve assembly then you don't need to seal up the holes around the top. From memory, I finally brazed the hole in the waisted part of the damper rod and redrilled a 2mm hole but to be honest, I've actually forgotten cos I tried so many different permutations..................  :hide:

There is a difference in spring and spacer size in later models

 

 

 

Thanks for responses.

So, I went with four slightly larger holes.

Kept emu preload as it was out of the the box, probably 2 / 2.5 turns?

Rotary valve was retained but holes were enlarged

Springs - have started with early TDM ones (2002-03 springs & trimmed down spacers).

Mixture of 10 and 15w oil, probably close to 12.5w, standard oil height.

 

Have to say she felt much better than the standard setup from the minute I took off up the road, bump compliance much better :) Springs are possibly a bit firm, even on minimum preload, so I'll either throw in my spare 0.85 linear springs or my 2008 standard springs with trimmed down spacers. Either way, this mod is well worth doing.

Just to sort the back-end out now ;)  




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