Shock techs please take a look

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2/9/2019 2:54 PM

I know this is not much, but can you see any differences between these two pics. Its off of an 83 cr250 i am restoring. I have two shocks for it. One has a pro circuit sticker on it and the other has a race tech sticker. They say a pic is worth a thousand words so I'm hoping you see something, thanks. Photo
Photo

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2/9/2019 3:16 PM

It looks like its missing half the valve stack on the bottom one

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2009 RMZ 250 (sold)
2004 LTZ 400
#nukethequads

2/9/2019 3:30 PM

That's a bunch of full size shims

And it lots like none on the rebound side.

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2/9/2019 3:31 PM

Radically different shim stack.

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THERE IS NO SECOND MOTO IN LIFE!

2/9/2019 3:33 PM

hillbilly wrote:

That's a bunch of full size shims

And it lots like none on the rebound side.

This is what I'm seeing too

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2/9/2019 3:43 PM

I have an 83 CR125 I bought a couple years ago for vintage mx. I changed the oil in the shock, and mine looked very similar. It looked like some sort of modification. From memory, I was thinking they turned down the end of the shaft and installed that collar with the drilled holes. I figured it was some custom design from some tuner in the past.

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Motocross....a once in a lifetime experience....every weekend.

2/9/2019 3:49 PM

It's some kinda voodoo. You need a witch doctor.

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If it ain't yer's don't take it, If it ain't the truth dont say it, If it ain't right don't do it...Marcus Aurelius

2/9/2019 3:54 PM

You're certain both of those are for an '83?

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2/9/2019 4:29 PM

The bottom one is likely going to be a much firmer shock. The top appears to have the clamp moved up and the stack of face shims underneath are essentially disabled. The rebound stack is recessed into the piston and there's not much to them.

You would have to take them apart and measure the shims to be more precise as to each set up.

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2/9/2019 4:59 PM

zehn wrote:

You're certain both of those are for an '83?

Yes, both off of 83 cr250

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2/9/2019 5:33 PM

Far different shim stacks

Without pulling down and measuring you wont know what each is like

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2/9/2019 6:18 PM

2 stage?

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2/9/2019 6:19 PM

This is an old school style compression stack where they don't taper the shims after the 1st cross over.
I had one like this work well but it was because there was a large bleed hole in the shock piston.

so the top one is a "dual stage" stack with a cross over in it.

The bottom one is a single stage stack.

Ride both and see which one you like... then adjust the stacks from there.

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2/9/2019 6:20 PM

cable wrote:

2 stage?

Was thinking that.

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2/9/2019 6:28 PM

PTshox wrote:

This is an old school style compression stack where they don't taper the shims after the 1st cross over.
I had one like this work well but it was because there was a large bleed hole in the shock piston.

so the top one is a "dual stage" stack with a cross over in it.

The bottom one is a single stage stack.

Ride both and see which one you like... then adjust the stacks from there.

If you notice on the bottom shock the valving washer next to the piston has notches cut in it. That is for low speed bleed(Shaft speed) .But yes, the top shaft has a dual stack, the bottom one is a straight stack.

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2/9/2019 6:46 PM

PTshox wrote:

This is an old school style compression stack where they don't taper the shims after the 1st cross over.
I had one like this work well but it was because there was a large bleed hole in the shock piston.

so the top one is a "dual stage" stack with a cross over in it.

The bottom one is a single stage stack.

Ride both and see which one you like... then adjust the stacks from there.

Going to rebuild with race tech bumber, seal, bushing. 10wt oil??. Would his gold valve be that much better?

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2/9/2019 6:54 PM

Mallet wrote:

If you notice on the bottom shock the valving washer next to the piston has notches cut in it. That is for low speed bleed(Shaft speed) .But yes, the top shaft has a dual stack, the bottom one is a straight stack.

Good eye, I couldn't see that until I blew up the photo, lol

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2/9/2019 7:15 PM

slipdog wrote:

The bottom one is likely going to be a much firmer shock. The top appears to have the clamp moved up and the stack of face shims underneath are essentially disabled. The rebound stack is recessed into the piston and there's not much to them.

You would have to take them apart and measure the shims to be more precise as to each set up.

I'm thought the opposite as the lower has a gap between shim stack and base plate from possibly a smaller clamping shim and about half way up the stack there appears a slight dark line or what I think may be a 0.10 crossover? Add in those bleed notches which is good pick up by Mallet who has obviously played with this voodoo back in the day?

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2/9/2019 7:19 PM

PTshox wrote:

This is an old school style compression stack where they don't taper the shims after the 1st cross over.
I had one like this work well but it was because there was a large bleed hole in the shock piston.

so the top one is a "dual stage" stack with a cross over in it.

The bottom one is a single stage stack.

Ride both and see which one you like... then adjust the stacks from there.

bad juju wrote:

Going to rebuild with race tech bumber, seal, bushing. 10wt oil??. Would his gold valve be that much better?

I think so that's where the GV's are a big benefit. Those old pistons had very small ports. Could benefit more though from a larger diameter body if possible.

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2/9/2019 7:59 PM

Straight stacks /non taper can oerform identically

However shim fatigue can be a problem so tapered stacks are better

You could modernize that shock with a newer style piston (maybe gold valve available that isnt from that era) and be really close to a modern shock

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2/10/2019 1:35 AM
Edited Date/Time: 2/10/2019 1:38 AM

slipdog wrote:

The bottom one is likely going to be a much firmer shock. The top appears to have the clamp moved up and the stack of face shims underneath are essentially disabled. The rebound stack is recessed into the piston and there's not much to them.

You would have to take them apart and measure the shims to be more precise as to each set up.

Underground wrote:

I'm thought the opposite as the lower has a gap between shim stack and base plate from possibly a smaller clamping shim and about half way up the stack there appears a slight dark line or what I think may be a 0.10 crossover? Add in those bleed notches which is good pick up by Mallet who has obviously played with this voodoo back in the day?

I didn't see those notches. Jim Lindeman used to do that once in a while back in the day. The problem, long term, is the shim with the notched will crack... split..etc. There is lots of stuff you can do to get the same effect. Placing a small diameter shim against the piston as the 1st compression shim and letting it bleed around it is one way. I've done that a lot on some bikes. I actually did that to the 16 KTM 350 XC F I have to get softer small bump compliance.

No need for a gold valve piston IMO. Work with what is there.

Curious how the shock body looks? And I would suggest lighter wt oil then 10.... Typical shock oil is 2.5 to 5 wt.

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2/10/2019 7:31 AM

new piston o-ring and piston band

2.5 to 5 weight as mentioned

check to see if the body is even anodized

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2/10/2019 10:36 AM

I've read somewhere in an old mxa mag that there was a mod for the reservoir hose to keep it from blowing off. They swapped a couple of shims and ran bel- ray 10wt i think. Gotta try and dig out that mag to see for sure. Also i have a simmons link for this as well. Which stack would you start with? Single stage or the two stage? Also the shock bodies are in great shape as are the shock shafts as well. Thank for the help and please keep it coming..

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2/10/2019 1:10 PM

If the shock oil recommendation is from way back then, then it may not be the best, time proven idea.

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2/10/2019 8:34 PM

My 84' cr250 shock , from new , would start having fading problems ( loss of control ) after 20 - 30 hours of usage
That time would shorten ...then after the 3rd oil change I bought an Ohlins
I guess I rode a lot

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2/13/2019 11:13 AM
Edited Date/Time: 2/13/2019 11:14 AM

I had an 87' CR125 shock that I rebuilt that had a similar 'straight' shim stack like that. They switched to a modern style valve stack in 88'.

Eric Gorr's book touches on the CR125 valving a little bit:

"SHOCK: The rear shock can be modified for better handling on the 1985 to 1988 models. These types of shocks use straight shims. The rebound valve stack has two transition shims, one in the middle and one closest to the piston. Put both transition shims between the number 26 and 27 shim from the piston. After this, the shock will handle square-edged bumps much better. "

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