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High speed adjustment on my shock?


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I understand the clickers on my shock... what does the high speed adjuster do? What traits in bike behavior can you address with this? I'm riding a 2007 YZ450 with Race-Tech gold valve kits and shim stacks front and rear for desert. I just installed heavier springs for my weight and re-set the sag. Much better... BUT... The rear end seems a little busy pounding through big whoops. I started with Race Tech baseline settings. Dealer advised playing with high speed first. I cranked up high speed 3/4 turn (in 1/4 turn increments) from baseline and it seemed to help. Then went to work on clickers. I am +2 fork comp, +1 fork rebound, +1 shock comp, +1 shock rebound. Feels really good (maybe as good as it gets), but like I said the rear end gets busy and out of line in big desert whoop sections. High speed adjuster info/suggestions much appreciated:worthy:

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the HS adjuster sets the preload of a backing plate behind the shim stack.

if the rod speed exceeds a limit, the stack hits the backing plate. now the spring preload of the backing plate allows the stack to open even more or not at the given rod speed.

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So from that, I gather that increasing HS damping adjuster causes the shock to damp more progessively with high shaft (rod) velocity. Backing the HS damping will decrease damping at high shaft speeds. This might be called speed sensitive damping versus shaft position (stroke) sensitive damping? I've heard that high speed damper adjustment can also affect dynamic sag or ride height in the rear?

So would turning the HS all the way in increase damping at all shaft velocities or just maximize damping when the shaft travels at high velocity?

Does this adjuster only affect the compression side of the stroke?

What's the best way to dial in this particular aspect of shock performance?

Many thanks!👍

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So would turning the HS all the way in increase damping at all shaft velocities or just maximize damping when the shaft travels at high velocity?

only at high velocity. at low speed the stack doesn't hit the backing plate. would be interesting what speed it needs to hit the backing plate 👍

so I don't believe HS has an influence in riding heigth

Does this adjuster only affect the compression side of the stroke?

yes, only compression

a few weeks ago I made a drawing:

http://www.supercross-online.de/Z/HS.gif

Edited by kawamaha
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Is the back end going side to side or straight up? My ktm was doing much the same as what you are describing i think, it was okay in smaller whoops but if I hit one deep/steep/fast whoop a little crooked the back end started swapping bad. Going in on the ls comp helped a little, havent messed with the hs yet. What actually ended almost completely solving it was reducing the shock spring preload by one turn. But, ktm's, especially with progressive springs, seem to like very little preload on the shock spring.

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The shock pre-load might be the culprit... I am running my sag at 99mm (w/o gear on). Maybe I'll take a spin off the spring and see how it reacts. Ran it there to try to keep more weight on the front to help the beast corner better. I tried running the high speed further out last weekend (2 turns out and 1-3/4 out) compared to 3/4 out and it worked ok in sand whoops that were spaced out longer, but tighter whoops it still wanted to buck straight up and out and had more tendency to bottom on bigger hits. Seemed to use more of the travel (felt too soft really), but also lacked control. Could probably tune most of that out with the clickers if I would have had more time before the race. I'm sure there's more than one way to skin this cat, I just haven't found the best way yet and am trying to get a handle on how to properly test/tune the high speed comp damper...? I would like to know the procedure a good tuner would use when working with a pro to dial in the best settings. Which adjustments to test first and in what terrain. A simple - If it does X adjust A+/-, but if it does Y, adjust B +/-. Then move to this terrain and work on...

I got the "dynamic ride height" bit out of dirt rider or MXA last month (I don't have the mag with me to confirm which mag/issue). They claimed the high speed adjuster would affect rear end height while riding - I assume this would be true in short choppy conditions where the high speed circuit would be involved in damping. I had never considered the HS adjustment to have any affect, but it sort of makes sense...

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From the limited experience I've had, the single biggest thing wrong with the YZ450 shock in the later years is the initial rebound response. The high speed piston can be improved by opening the ports a little, but the lack of initial rebound is what makes the back of the bike act up. If you crank down on the adjusters, you get the initial that you need, but then the damping is too heavy on deeper strokes, and it will pack.

On my '06, we replaced the first 7 36x12x0.15 shims with 36x12x0.30's, and did nothing else to the shock. I'm using Dave Johnson's 215.VM2.K5 fluid at 145 psi of N. The improvement in the behavior of the back of the bike was phenomenal, even to the extent that the front behaves better because of it.

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No much really.

before I had a closer look at it, I thought it would act like a blow off. instead, it works as a limiter 👍 not a good idea IMO...

I don't have complaints about the rear, otherwise I would thinking of change it to a blowoff

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