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Revalving a 5th gen fork for better rebound


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I have a 2000 5th gen with Gold Valve compression valves and would like to utilize the stock rebound valves because I have too many other things I need to spend my money on, including a recent traffic award, and instead utilize the extra shims I already have. Having said that, can anyone suggest a shim stack for a 1.00 fork spring? I recently added 2 15x17 shims to the original stock shim stack and I'm thinking it's still to fast using Maxima 5wt oil. I'm considering adding 2 more to the stack but would like to minimize the amount of time I pull the forks and only do this once more. So, got any suggestions?

 

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  • Baroquenride changed the title to Revalving a 5th gen fork for better rebound
  • Member Contributer

Thermosman used 7W in my 5th gen forks, FYI. 

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Branded oil weight unfortunately doesn't mean much, you need to determine proper oil by centistoke or cSt rating. 

 

Have a look here: https://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid

 

Traxxion recommended Maxima 7 125-150 oil when they built my shim stacks for my Racetech G2R comp and Traxxion rebound valves. The Maxima oil has a cSt of 26.70, which I was pleasantly surprised to find very close to the 50/50 SS-7/SS-8 blend I was using before (cSt of 26.455)

 

 

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You will be hard pressed to improve the stock rebound on 5w oil. 7.5w as a minimum would be best.

 

When you say 1.0 weight spring I assume that is Kg/mm. IIRC the stock spring is about .75Kg/mm so the damping as stock is set for that weight spring & usually to soft. So you will need heavier oil or a far stiffer shim stack. 

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On 5/27/2022 at 10:35 AM, Mohawk said:

...or a far stiffer shim stack. 

That's what I'm going for is a stiffer shim stack and looking for advice from folks that have done it. 

 

Guys, I've already played with oil weights in the past and came up with what works for me using the stock components. Now that I've got a Gold Valve compression valve which calls for a thin 5wt fluid according to Race Tech, I'm using that as my base fluid and hoping to match the rebound side of things by revalving it stiffer. The stock rebound shim stack is as follows:

valve
10x17
10x16
10x15
20x8.2
40x11.3

I'm proposing using the following shims to get where I think I want to be:

valve
(2) 15x17
(3) 10x17
(3) 10x16
10x12
20x8.2
40x11.3

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I'm guessing if Racetech specified a 1kg spring rate you and I are around the same weight.  I will see if I can dig up what Racetech specified for my gold rebound valves but that was a looooooong time ago and I don't think I have it anywhere.  Also, the Racetech piston ports are a lot different than the stock ones, that's part of the magic.  They shift a lot more of the damping from orifice restriction (hydraulic choking) to the shim stack.  So maybe start something less than what goes with the gold valves.

 

FWIW I don't recall stock rebound being as terrible as stock compression valving.  The Racetech setup opens up high speed compression a lot so square edge hits and potholes are much, much smoother.  

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Aaaand I don't have it anywhere.  I think I bought my kit from a local suspension shop which no longer exists, but they gave me a lot of advice and even checked my assembly before I put my fork back together.  Maybe call some Racetech vendors and see what they suggest with the stock valves.

 

One thing they suggest which wasn't in any instructions - polish the damper rod with steel wool, etc. while you've got it apart.  There's a lot of seal drag in the damper and this reduces it significantly.  Good luck!

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Thanks for the help ShipFixer, yeah I agree on the logic about the ports in the stock valve being much smaller therefore not using quite the same shimstack as the comparable Gold Valves. I figure with the Maxima 5wt at 15.9cst@40C and the smaller holes, along with just the right shim stack I can make it all work. I just wish I had access to a shim stack program.

 

So I put it all together today and ended up adding a .10x15 shim in the stack and overall it seems to feel much better than the last iteration! I really don't understand why Honda added the 2 super thick shims in the bottom of the stack and I may take those out. With the thickness of the shim stack the nut doesn't have as much to hang on to and even though it's held on by red loctite, I'd feel better if the shaft were flush with the end of the nut at least. Actually, I think the 20x8.2 shim is a fulcrum which needs to be there and the 40x11.3 is a spacer shim which I'll take out the next time I play with it.

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  • 3 months later...
I finally had a chance to work on the forks this week and I think I finally found the right combo or damn close!

I added 3 more .10 x 17 shims as that's what I had on hand. So now I have this combo on the rebound side using the stock Honda valves:
(2) .15x17
(6) .10x17
(3) .10x16
(1) .10x15
(1) .10x12
(1) .20x8.2
oil is 130mm from the top

I took out the 40x11.3 as that was just a spacer that I didn't need. I also used a combo of Maxima 5wt and some Maxima 15wt in a 75%/25% combo as I had both on hand. I didn't measure accurately, AND I spilled some out on one fork so that is just what I was going for and may have something else at the moment. So after a 20 min ride tonight on bumpy pavement, my forks feel comparable to my Penske shock out back and the bike feels well balanced, smoother, and not nearly as bouncy up front as it was. Moreover, it feels better than the stock valving finally! I'm still going to try an official Maxima 7.5wt oil to make sure I'm using an honest 7.5 weight but I'm going to run this as is, for several months I think. I'll report back once I swap it out down the road.
 
 
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