Stock Fork is Cartridge or Damping rod

[mcsahib]

Want to resprung and re-valve the stock (non cup) front fork. Anyone who 've done the upgrade can tell me whether it is cartridge or damping rod?

 

[gbabyracing]

A very basic cartridge.

 

[SPG]

It is a Big Piston Fork style, but the damping is provided by the holes in the piston and some checkplates instead of a tunable shim stack. Strangely, my fork was not bad on the track once it was resprung, a little 10wt oil, and the oil height raised 15mm or so. The shims are listed as 14mm (check plates), but the shims run on a sleeve, so you would need to make a new stepped sleeve to run a conventional 14mm shim stack.

GP suspension says they are working on a rod and piston kit to keep the BPF, but have a conventional shim stack and better valving characteristics.

-Sean

 

[gbabyracing]

Sean - Like you, I found that with .85 or .9 springs, proper preloading, and 7wt oil - the front was quite good. I've wondered if playing with those two shims you could effect HS damping? I say for a lot street and some TD riders, springs and oil are all you'll ever need when coupled with a decent shock.

 

[SPG]

Sean - Like you, I found that with .85 or .9 springs, proper preloading, and 7wt oil - the front was quite good. I've wondered if playing with those two shims you could effect HS damping? I say for a lot street and some TD riders, springs and oil are all you'll ever need when coupled with a decent shock.

I'm pretty sure the HS damping is limited by orifice size at this point. Since the check plate springs are very soft, they open up almost immediately. I would suspect that with a normal shim stack you could open up the ports and have more compliant high speed travel while maintaining the low speed support for braking and reduced weight transfer in transitions.

FWIW, last weekend the .80 springs, 10wt oil front and 700lb spring and re-shimmed shock worked quite well. When I rebuilt the shock, I added 3mm in length. With these changes I set the preload at 7/10 to get 30mm sag at the rear. On the track, it would run wide mid-corner, so I went to 8/10 preload which stopped that. Finally I went 9/10 on preload and it now finishes the corner nicely, tightening the line as throttle is applied. It's stable on the brakes and tire wear is good. Overall, I'm pretty happy with it.
-Sean

 

[mr-fabricator]

Shaun , when u say re shimmed rear shock can you explain what u mean please ?? Are you playing with valve sizes ?? Also what oil are u re filling the rear shock with .

With regards to the front are you using straight 10wt or a blend , i was going to try 6 or 7 wich is a jump from the factory 4wt so 10wt seems pretty high , also im 180lb ish (80kg ish ) in race gear and my bike is 147kg track side , what front springs would you suggest . I do ride the front hard so was looking to put 0.9 in the front .

Thanks in advance

 

[SPG]

Hi Lee,
A wild guess on my end would be .85-.90. I'm about 170 in gear and the .80s seem good with 15mm of preload. If you are a touch heavier and want a firmer front and maybe a little less preload, the .85s could be a good start. The fork oil in the US bikes is 5 wt, so 7 or 10 would be a little step up, but I wanted to add some support for braking and increase the rebound to match the stiffer spring.

For the shock, it is filled with 2.5wt and I stuck with that. I left the valving (piston) alone and changed the shim stack on the compression side of the piston. I left the rebound damping alone. Somewhere else on this forum, someone posted the WP build sheet with the shim stack (and oil wt, height, etc). On the compression side, pretty much all the .15mm shims were changed to .2mm and the smallest 4 .2mm shims were changed to .3mm. Finally, the 17mm clamp shim on top was increased to an 18mm. Put back together, recharged with 235psi of nitrogen and good to go.

-Sean

 

[Bagwell]

SPG, was this on the CUP bike or street bike? I think we all forget to be clear about which model we are talking about sometimes. I know both have different suspension on em.

Thanks,
Vaughn

 

[Formula390]

SPG, was this on the CUP bike or street bike? I think we all forget to be clear about which model we are talking about sometimes. I know both have different suspension on em.

Thanks,
Vaughn

From description, totally sounds like he's got a cup bike. The stock OEM shock on the street bike can't be rebuilt at all, just a spring change... so given he's talking about valving, dampening, compression stack, and changing the oil weight, no way that is the stock shock (pictured below):.

 

[Formula390]

Addendum. Image uploading is PARTIALLY working. If you upload via URL and do NOT select "Retrieve remote file and reference locally" then the Insert Image process works. All other forms of inserting an image fail:

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Scenario 1: Insert Image - From Computer - Advanced Dialog - FAIL

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Scenario 2: Insert Image - From Computer - Basic - FAIL

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Scenario 3: Insert Image - From URL - Retrieve remote file and reference locally - CHECKED - FAIL

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Scenario 4: Insert Image - From URL - Retrieve remote file and reference locally - UNCHECKED - URL is a standard URL to a SMALL image like https://photos.google.com/u/1/album.../AF1QipOVeDiasJ9KjTBBymFwLnAUoYi7IKzpnsmOMjPY - Success

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Scenario 5: Insert Image - From URL - Retrieve remote file and reference locally - UNCHECKED - URL is a standard URL to a LARGE image which requires the sites resizer be used like https://lh3.googleusercontent.com/UihuhO9l9JrYlEfFW-ydbIV0PT9JDMiwADC-iFbs-w=w1593-h896-no - Success

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Scenario 6: Insert Image - From URL - Retrieve remote file and reference locally - UNCHECKED - URL is a redirect URL like https://goo.gl/photos/DxVu1TTWxUeGueb38 - FAIL (get broken image thumbnail)

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[SPG]

Hi Matt,
Incorrect. It is the street bike. I have the cheapo, non-adjustable shock you have pictures. Only difference, is next to the top eye, I have drilled and tapped the body for a schrader valve which comes off at about a 45 degree angle to the shock. This allows for continued nitrogen draining and refilling. The first disassembly required drilling the top with a 1/16 hole (and safety glasses) to let the gas out. This hole was later enlarged to fit the valve. Once drained, the lower cap comes out with a drift punch, and the seal head is pushed in, and a circlip removed before it is drawn out with the shaft assembly.
-Sean

 

[Formula390]

Hi Matt,
Incorrect. It is the street bike. I have the cheapo, non-adjustable shock you have pictures. Only difference, is next to the top eye, I have drilled and tapped the body for a schrader valve which comes off at about a 45 degree angle to the shock. This allows for continued nitrogen draining and refilling. The first disassembly required drilling the top with a 1/16 hole (and safety glasses) to let the gas out. This hole was later enlarged to fit the valve. Once drained, the lower cap comes out with a drift punch, and the seal head is pushed in, and a circlip removed before it is drawn out with the shaft assembly.
-Sean

Ahhh! Well that's certainly an ambitious method of reworking the stock shock to be sure! I suspect that's well outside the bounds of what most would feel comfortable with doing, but glad that method is working out. I'm pursuing the 99-02 R6 shock swap method. That shock is far easier to get into and rebuild/revalve. So far tho it's looking like revalving won't be necessary for the R6 shock as it's adjustment range seems well within the bounds of what we'd need on the RC390 once we get a good spring on it.

 

[SPG]

True, it might not be for the average owner to rebuild. That said, if you were to take it to a suspension shop, they do this type of thing every day. Honestly the only reason I did it is to see how far I could take the stock suspension; now that I know, I'm glad I did

-Sean

 

[reenmachine]

Hi Matt,
Incorrect. It is the street bike. I have the cheapo, non-adjustable shock you have pictures. Only difference, is next to the top eye, I have drilled and tapped the body for a schrader valve which comes off at about a 45 degree angle to the shock. This allows for continued nitrogen draining and refilling. The first disassembly required drilling the top with a 1/16 hole (and safety glasses) to let the gas out. This hole was later enlarged to fit the valve. Once drained, the lower cap comes out with a drift punch, and the seal head is pushed in, and a circlip removed before it is drawn out with the shaft assembly.
-Sean

True, it might not be for the average owner to rebuild. That said, if you were to take it to a suspension shop, they do this type of thing every day. Honestly the only reason I did it is to see how far I could take the stock suspension; now that I know, I'm glad I did

-Sean

Photos and description of what you did, how you use it, and what it did for you would make a great thread of its own if you're so inclined.

 

[SPG]

Photos and description of what you did, how you use it, and what it did for you would make a great thread of its own if you're so inclined.

Being lazy, I just looked to see if someone had done a better job already What follows is a link for a reservoir shock. The stock RC shock is easier in the disassembly, and then for the reassembly you turn the body upside down in a vice, fill it with oil to 58mm below the edge of the body, and insert the shaft assembly back into the body.

The second link is a KLR non reservoir shock, which is similar to the RC through disassembly. They chose to refill the oil after putting it back together, which would not apply to the RC shock.

Once the body is drilled and tapped for the schrader valve, it is a pretty quick operation.

-Sean


https://www.youtube.com/watch?v=0_InEnom2ec

https://www.youtube.com/watch?v=A0tcKkevRH0

 

[Bagwell]

Yeah, I have heard of this work being done to seemingly non serviceable rear shocks, but I had never done one before.

 

[mr-fabricator]

Great work sean , i will be printing off all this info for a suspension guy to follow as for club racing i can not swap out the rear shock , cant even use the cup shock . Im also playing with the r6 shock wich i can run in thunder bikes , front forks ill fill with firmer oil and try out this weekend with the stock springs . Then purchase some 0.9's im a little heavier than u and tend to push the front of my bikes quite hard .

What are the dimensions of the front springs ? Or what other bikes fit ? I can make up spacers at work ..

 

[SPG]

36mm diameter x 250ish... The '09-'11 zx6r is supposed to be a match. anything from 230-320mm will probably be fine. If you shoot me a PM to remind me, I can try and dig up exactly what I did for the shims.
-Sean

 

[mr-fabricator]

Thanks mate . Will throw u a pm .

 

[Formula390]

36mm diameter x 250ish... The '09-'11 zx6r is supposed to be a match. anything from 230-320mm will probably be fine. If you shoot me a PM to remind me, I can try and dig up exactly what I did for the shims.
-Sean

PING!

230-320 seems like an awfully HUGE range. What is the length of the stock springs? (yeah... lazy... I haven't pulled the front end apart yet... been working on... other stuffs! LOL)