Honda hpsd service

Kawasaki-rider
Edited Date/Time 3/23/2021 12:37pm
So I have taken apart an old hpsd to learn..
This one is going on my 125 after some mods.
I got some questions:

I'm assuming it's using fork fluid.
When you fill it up, you fill thru the adjuster screw hole, then bolt on the adjuster?

Have any of you played around with valving/shimstacks and/or different fluid?

Thanks!

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slipdog
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slipdog 11/4/2016 7:31am
11/4/2016 7:31am
I fill them with the adjuster in, install the separator piston/spring and the main shaft. There will be too much pressure to fully seat the seal head and that's when you crack the adjuster open to allow the excess fluid to bleed out as you sink the seal head the last little bit and secure the main circlip.

Due to the excess bleed through the bypass and the main piston they don't have much "feel" to them and I found using 30wt fork oil and epoxying the piston bleed hole closed will get it to feel the most like a regular damper
Charper732
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Charper732 11/4/2016 10:07am
11/4/2016 10:07am
I did the race tech revalve on mine. It made a huge difference.
Kawasaki-rider 11/4/2016 11:20am
11/4/2016 11:20am
So basically adjuster all the way in, fill thru the main piston hole, assemble spring side, then assemble piston/seal head and open adjuster for the last bit?

I'm assuming it should be completely full with fluid and no air, that would make sense with your style of filling it up.

Epoxy piston bleed, do you mean this hole:



slipdog
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slipdog 11/4/2016 2:31pm
11/4/2016 2:31pm
Yes you're correct on the assembly process. The bleed hole in the piston is the one I close with epoxy, not the bypass port for the adjuster. Look closely at the piston and there is a small hole in one of the compression ports just above the piston's sealing band.

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slipdog
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slipdog 11/5/2016 10:28am
11/5/2016 10:28am
Yes, that's the one. I use a small file to rough up the port ledge the hole is in and use rubbing alcohol to make sure the epoxy anchors itself really well. I have never seen the Gold Valve or any other replacement piston for the damper, but I would guess the piston bleed in the Gold Valve is reduced or non existent as well.

It's what I found gives it a much stronger damping feel and much more sensitivity in the adjuster, but I do have a lot of experience using epoxy so I'm comfortable doing a mod like that.

FWYT
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FWYT 11/5/2016 11:36am
11/5/2016 11:36am Edited Date/Time 11/5/2016 11:37am
Slipdog knows his stuff FAR more than myself but I'll add-
I just submerge the whole unit in a small, shallow pan when bleeding.
That way it can't suck any air back in. I just thickened up some fork fluid
with some motor oil till it felt, oh you, know, just about right. Science!!

(Slipdog is probably doing a total *face-palm* right now. hahahha)

I didn't mess with the stacks or the ports; just got the oil viscosity to about
where it feels good and called it done.
slipdog
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slipdog 11/5/2016 12:08pm
11/5/2016 12:08pm
FWYT wrote:
Slipdog knows his stuff FAR more than myself but I'll add- I just submerge the whole unit in a small, shallow pan when bleeding. That way...
Slipdog knows his stuff FAR more than myself but I'll add-
I just submerge the whole unit in a small, shallow pan when bleeding.
That way it can't suck any air back in. I just thickened up some fork fluid
with some motor oil till it felt, oh you, know, just about right. Science!!

(Slipdog is probably doing a total *face-palm* right now. hahahha)

I didn't mess with the stacks or the ports; just got the oil viscosity to about
where it feels good and called it done.
Actually, before I started modifying them the first thing I did to the one on my '08 crf was to put Rotella in it. It definitely gave it a more solid when you turned the bars.
slipdog
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slipdog 11/5/2016 12:14pm
11/5/2016 12:14pm
Also, when just assembling it I seen no reason you cant fill through the adjuster. I was just stating how I fill them not meaning it's the only way to do it.
Kawasaki-rider 11/5/2016 12:53pm
11/5/2016 12:53pm
Thanks man!
I'll use this hpsd for experimental stuff, so I'll try epoxy it!

Would be cool to later make the holes in the piston larger and/or close em up, to see what it does. Will play around with it on my 250f at first. Smile
Slosh 112
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Slosh 112 11/10/2016 1:24am
11/10/2016 1:24am
Have you tried the 22mm damper off a later model?? Ive got one on my RM125 and didn't think it did anything until I removed it and went for a ride. Its small but I noticed it when it was removed. I'm going to play around with mine too once I get the bike dialled.
Kawasaki-rider 11/10/2016 1:42am
11/10/2016 1:42am
What year did they change? Got one on my 16 crf also, stock at the moment.
Tuplis
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Tuplis 3/23/2021 12:37pm
3/23/2021 12:37pm
Old topic, but does anyone know if that shaft seal can be replaced? Mine is leaking...

Cant find it from anywhere and Honda offers only complete piston for too much money
Size is 8x17x?

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