Bouncy shock after rebuild help

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1/12/2019 5:40 AM

Any folks do their own shock work?
Ran into an issue. I rebuilt a shock and its bouncy as hell(was bouncy prior to servicing,however then it had almost no oil or air in the bladder). Shock head was replaced. Piston band looks good. Adjusters were cleaned. Bladder was charged at 150psi nitrogen and did not leak. What else could cause the shock to be bouncy. It feels as though there is no reisistance. Shock body is undamaged of which i can see. Its on a 98rm80.

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1/12/2019 5:58 AM

Turn in rebound adjuster, see if that helps, no burrs or scratches in shock shaft, piston was installed correct.

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1/12/2019 6:04 AM

Tried turning both adjusters all the way in and out. Felt no.difference. piston and shims were installed exactly as it was removed.i used a screw driver to.hold all items in the proper order. Unless the previous owner messed with it. Highly unlikely though. Not sure wat else it can be

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1/12/2019 7:04 AM

Which side goes up ? Photo

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1/12/2019 8:01 AM

1st pic is the compression side which takes the shim stack with the larger diameter shims. The 2nd is the rebound side, that is the "top" or goes up The shim stack with the smaller diameter shims goes there then the washer and finally the nut that holds it all together.

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1/12/2019 8:04 AM

If it was out of oil when you took it apart the shock body may be worn out.

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1/12/2019 8:07 AM

slipdog wrote:

If it was out of oil when you took it apart the shock body may be worn out.

It could be. Do you think a worn piston band may allow the fluid to bypass the piston itself? I have not changed the band.

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1/12/2019 8:19 AM
Edited Date/Time: 1/12/2019 8:22 AM

Yes, if they are run with low or no oil the piston overheats and the band wears to the point of no seal and that leaves the metal piston itself to rub against the aluminum shock body wearing it out.

If you have a bore gauge you can take a measurement at the top, bottom and middle of the body. If the middle is more than just a few thou larger than the very top and bottom it may never seal well even with a new piston/band. I've seen that a lot with vintage shocks from the 80's.

It's hard to diagnose a problem like you have over the internet though. My first thought os like Kristen said and the piston or shim stacks gor flipped.

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1/12/2019 8:27 AM
Edited Date/Time: 1/12/2019 8:28 AM

Although... that piston design looks like if you got them upside down it would hydraulic lock instead of losing all damping.

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1/12/2019 8:54 AM

Here is my shim stack.left is bottom all the way up to the nut.also is the shock head. Gonna try to measure the barrel Photo
Photo


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1/12/2019 9:04 AM

Bore is smooth .no marks to suggest damage. I measured it in 4 places and it shows 33mm. Ah this is so confusing. Tha ks for all the help thus far
Photo

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1/12/2019 9:26 AM

Yes, that was all installed correctly. Measure the piston band with some calipers as well. It should be over 33mm. usually, XX.15mm is considered service limit on piston band size but even when I see them undersized like at 32.85 or so they will still dampen and not be a pogo stick. Over time with heat cycles the O-ring underneath the Teflon piston band deforms and goes flat or become square instead of round, that's what causes the loss of size/seal more than the band itself wearing down but you can't replace the O-ring without cutting off the band first.

I would assume in your case something else is going on.

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1/12/2019 9:32 AM

Piston band is almost exactly 33mm.i thinks it really is too worn piston ban and faiming orings l. I would close off this job here. I cant even seem to find showa 33mm piston bands. The band itself feels brittle. Tbh it looks like the oem one.

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1/12/2019 10:13 AM

What year /bike is that from, I believe #4 and # 5 should be it from this '02 RM85 but my memory is not 100% on what year they switched to the new style piston.

https://www.bikebandit.com/oem-parts/2002-suzuki-rm85-rm85k2/o/m147697#sch281082

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1/12/2019 11:09 AM

4 and 5 seems to be the oring onthe shock head and circlip on the shock body. The bike is a 98 rm 80. I reinstalled eveything and will.get my light nephew to bump on it. If all esle fails i will look into using a heavier oil. Im using light 5 atm.

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1/12/2019 12:07 PM

KILLASAN wrote:

4 and 5 seems to be the oring onthe shock head and circlip on the shock body. The bike is a 98 rm 80. I reinstalled eveything ...more

You're right that #5 is definitely a circlip now that I look again. None of the Honda parts lists I looked at had piston parts available either and unfortunately, there's no direct Showa supplier to contact for that.

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1/12/2019 3:04 PM

Did you use a seal head tool or plastic bag when installing seal head over shaft, sometimes they get cut

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1/12/2019 3:51 PM

Kristen_Valentino wrote:

Did you use a seal head tool or plastic bag when installing seal head over shaft, sometimes they get cut

Used some electrical tape. My bullet doesbr fit that thin of a shaft. However you can feel the ease during the rebuild. It doesnt have the force/suction when pumping the shaft. This is before setting the shock head.

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1/12/2019 10:43 PM

Make sure it has nitro in it...can leak out and cause it to be springy

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IG @jaredkeller96

1/13/2019 1:37 PM

I bet the piston band o-ring is shot to hell. As slipdog mentioned, they wear out underneath the piston band.


Look for Honda 52431-GC4-003 (unavailable). It is 33mm and might work.

Do a notch cut to get that band off and install a new o-ring.

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1/13/2019 2:21 PM

Maybe air in the shock still somewhere?

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1/13/2019 2:34 PM

KDXGarage wrote:

I bet the piston band o-ring is shot to hell. As slipdog mentioned, they wear out underneath the piston band.


Look for Honda ...more

I highly suspect the same thing. Thanks for the part no. What bike would that be off?

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1/13/2019 5:19 PM

Not sure if it fits, but worth a try

1989 - 1994 CR

Check years, not sure

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1/14/2019 5:28 PM

Good news . Called factory connection and they have instock. Just ordered hopefuy solves the issue

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1/15/2019 3:52 AM

Great news!

Did you get an o-ring too?

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1/15/2019 4:11 AM

KDXGarage wrote:

Great news!

Did you get an o-ring too?

Definitely!!

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1/15/2019 8:53 AM

Sweet! Thanks for letting us know you found one there. I have heard a few people comment that Showa parts are harder to find than KYB. I know with KYB Technical Touch, the last ten years have made it easy to find most KYB parts.

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1/15/2019 8:59 AM

KDXGarage wrote:

Sweet! Thanks for letting us know you found one there. I have heard a few people comment that Showa parts are harder to find ...more

That indeed is true. Showa parts are not readily available. I had recently restored a 92 rm and could not find a bladder anywhere. Even tried buyin a kyb one similar sized. (Didnt work as bladder shaped differently). Guys at fc responded and had 2 instock. Any parts i cant find it seems they got it. Now i just hope this solves my issue. Thanks guys ill report back wen i get it installed.

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