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Rebound Seperator Nut?


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In order to optimize the rsv, at a minimum you need to run lighter rebound damping. The rsv provides pitch control when on the brakes that would normally be accomplished, in part, by heavier rebound damping in the shock. So by running the rsv you can enjoy the traction benefit of lighter rebound valving. We also ran lighter compression valving due to the restriction in free bleed. This was in a motocross application on an 08 KX250F. I received the valving specs from Terry Hay.

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  • 3 years later...

Anyone using these for high speed offroad (D37/desert)? Finding the rear end of my YZ is always bouncy/pitchy no matter what because of the huge freebleed. Doesn't help me much in g-outs or rolling terrain.

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250 2T chassis.

I had the SPI setup in there before, and removed it a while back. That rebound valving made things worse. To get any kind of traction you had to run the rebound adjuster >10 clicks out, and that made the LSR/LSC bouncy as all hell. That and the compression valving on those kits is WAY light, both on the main piston and the exchange piston. Dangerous for racing, but felt OK if I were just putting around and never stood up while riding.

Those shocks need to be valved for an adjuster position of 4-8 clicks out for any reasonable LS support, or have something done to address the excessive bleed. I'll try one of these separator valves next, but not sure which one (closed, small bleed, larger bleed). There seem to be options from Race Tech and MX tech.

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So I went from the SPI exchange stack with the bored out ports back to the stock stack with the bored out ports and had the back end sitting a lot higher in the travel through repeated hits. I lost some initial plushness on a single hit, but when staying on the gas through repeated hits, that single change kept the rear end much more under control, and allowed the HSC adjuster to be run 1/4-1/2 turn further out without getting super bouncy.

The rebound on this shock still needs work. Through the few sets of valving that I've had on it, the bleed has always been the issue. I've never had these problems on the Showa stuff that I also run. That's why I want to try that sep nut next.

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I found that was one of the main sources of the loose bouncy feeling of the rear end of my YZ. Going to try the separator nut next, and then see if there are any other small changes to be done in the exchange stack for some more mid-speed support without getting harsh.

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Hey gray, above you said that you lightened the entire stack...do you use the (or similar) 9x.2 bleed or lead in shim? Im trying to figure my next step after I get test ride. What does this mostly affect? Smoother transition from low to high or am I missing something else it may do?

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The entire stack was lightened by using thinner shims. At first glance, it doesn't look like anything was changed outside the 9, but one .30 mm shim is slightly stiffer than 3 of the same size .20's, so it's a significant change.

The 9 is NOT a bleed shim. The first 18 will still be in direct contact with the 21.5 x .80 x 17.5 seat shim when the valve is closed, but the 9 takes a little pressure off of it so it opens sooner.

The effect I was looking for was increased compliance over ~4" rocks at low bike speeds, and this did help. It may not suit everyone, though. For my purposes, I haven't found a downside.

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Installed the separator nut on the shock this weekend (bike is apart for a full top/bottom end at the moment) but the shock action by hand is STIFF on the low speed. It's going to be very interesting to see how it rides. I'm predicting the front end traction in corners is going to be vastly different.

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