Highspeed bumps killing my kidneys: rear shock

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strider80
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Highspeed bumps killing my kidneys: rear shock

Post by strider80 »

So, now that my KX frontend is pretty well dialed and my arms are not taking a beating on braking bumps, my attention has been diverted to my aching back from the hits coming through the shock. The area I was riding this weekend had a lot of stretches of what I call braking bumps, even if they were not in the braking areas.

The shock feels great on lower speed hits, but the little 6-12" bumps spaced 1-2ft apart really tire me out due the sharp shocks my body is taking, even at slower riding speeds. My shock has been freshly serviced and was revalved by FRP a few years ago (I was not really knowledgeable about suspension at the time, not exactly sure of the shim stack setup). I backed out the compression adjuster 6 turns from my nominal, that made the bike ride more like a caddy down the trails, but the highspeed bumps were still pretty bad.

So here are my options I am thinking about
Revalve what is there with a new stack (any suggestions?)

Install aftermarket valving

Buy a KX or Showa shock and have it modded to fit the KDX.

Anyone else get to this point of having the KX front end dialed and realizing the shock needed work?
Last edited by strider80 on 01:54 pm Jul 02 2007, edited 2 times in total.
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Jeb
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Re: Highspeed bumps killing by kidneys: rear shock

Post by Jeb »

>|<>QBB<
strider80 wrote:
. . . Anyone else get to this point of having the KX front end dialed and realizing the shock needed work?
I just got through servicing mine - seal/wiper/oil & repressurized - and it made a big difference, but that was because it was in such sorry shape to begin with. I did find that compression/rebound adjustments now have a more pronounced effect.

What was the last time you had your serviced? Many suggest once, twice a year depending on use.
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Post by krazyinski »

Got to ask how long has it been sense you looked at the rear shock bearing,where the shock bolts to the linkage? that or just your shock needs service is more like to be the culprit. I have had mine re valved and she runs good. I had an issue with harshness that I could not adjust out and the locked up bearing was to blame. shock did fine on big stuff but the small junk was erratic and I couldn't adjust it out. After installing the new bearing all was good.
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Post by kawagumby »

Are you using the right spring for your weight? If you're less than 180 lbs, the stock 5.0 is just too stiff. Makes BIG difference .... and once you have the correct spring, you can dial a stock KDX shock to work very well.
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Post by hockeyboysomers »

I'm noticing the same problem with my 220. I installed KX forks over the winter. The forks are great! They seem more solid, less wander, less arm pump, no underhang. Maybe because I'm now going faster the back is all over the place. If I hit bumps or big rocks and I'm sitting on the seat I get a painful jolt up my spine. I've tried messing with the clickers but have not come up with a solution yet. I'm also thinking of having the rear shock rebuilt. I used to think the forks were limiting my speed through tough sections, now I feel the rear is.
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Post by KarlP »

I second the thought to look to the linkage. That little tiny bearing at the bottom end of the shock doesn't seem to last more than 3 or 4 months when I'm riding 6 or 7 hours a week. Things get really harsh over small stuff at speed when that bearing starts to go out.
I also blamed the shop for not servicing my shock right and it turned out to be the swingarm bearings. It was getting really stiff over the larger hits at speed. The swingarm movement felt fine when I just moved it up and down with the shock off. When I pulled the swingarm bolt out I found water had gotten to both outboard bearings, they were half-way completely toasted.

With new bearings where needed my rear suspension is working great again.

I'd look at all of your linkage bearings thoroughly. There should be no free play anywhere in the rear suspension when your bike is up on a stand and of course all bearings should be loaded with grease, not rust and water like mine.
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Post by strider80 »

The shock was serviced about 20 hours ago(2 months ago), all the bearings were replaced 40 hours (last winter) ago or so. Probably should check them again.

The spring is stock, and I weigh about 210-215 geared up.

Does Nitrogen pressure affect harshness?
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Post by crazybrit »

>|<>QBB<
KarlP wrote:I second the thought to look to the linkage. That little tiny bearing at the bottom end of the shock doesn't seem to last more than 3 or 4 months when I'm riding 6 or 7 hours a week. Things get really harsh over small stuff at speed when that bearing starts to go out.
Next time I do mine I'm going to upgrade to that bearing that CC found. Needs a little machining but the stocker isn't very good.
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Post by KarlP »

Yeah, I wouldn't mind an update on how that arrangement is holding up. The stocker is just not up to the job, in my opinion.
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Post by IdahoCharley »

Nitrogen pressure low or rebound set too stiff will cause shock packing in the type of bumps your describing.
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Post by Colorado Mike »

I thought my stock shock was junk after swapping to KX forks. Turns out it was. Cuz it was blown out. If your's is really that bad, I would have to question the rebuild job, mostly because nearly anytime I have someone do some work for me they illustrate just how big of a brain dead zombie they really are. Or maybe you are just a really good rider and ought to upgrade to an RM shock.
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Post by strider80 »

The mechanic who rebuilt it was me ( I am fairly competent, but no expert for sure), and I had a shop charge it for me. I could have screwed up the job, but I was pretty careful and only removed the piston and bladder, I did not disassemble the piston. The shop could have not put in enough nitro though.

The weird thing is that it feels great everywhere except for those bumps. I may pull it out and at least feel the shock to see if the charge is gone.
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Post by canyncarvr »

Re: 'Nitrogen pressure low or rebound set too stiff will cause shock packing in the type of bumps your describing.'

Your description does sound like a 'packing' issue..the shock doesn't recover before it gets hit again.

Too SOFT a compression setting will do that, too.

My shock was revalved a long time ago..so I cannot comment much on how the OEM works or doesn't. I don't recall clickers making as big a difference on the original setup..but they DO matter.

What are your sag settings? Start there...clickers set afterward.

My shock has been serviced (and valving changed a few times) by Ridhard Wilson...House of Horsepower in Eugene OR. What a huge treat it is! The amount of movement the shock swallows up amazes me. How it can be so supple, yet effective, strikes me everytime I ride. WELL worth it!!

Re: 'That little tiny bearing at the bottom end of the shock doesn't seem to last more than 3 or 4 months when I'm riding 6 or 7 hours a week.'

Amen. The double sealed bearing I use now changed that interval to a year or more. Actually, it's been over a year since I put one in..thought it was headed south because I could feel a loose 'tick' in the backend. But...it's wheel bearings.

Time to change them out for a FREE set from CBR!!! They last 2-3X what the cheap crappers do, too. I've got a brandy new NSK set all ready to go!!

Re: Shock charge

Don't test it with a gauge. Not much volume..one 'pfftt' and you just lost a good bit of nitro. Well...you know that......call me Mr. Obvious. :wink:

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strider80
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Post by strider80 »

What is the part number for that bearing?

I will take the linkage apart and check out that stuff, then feel the shock for gurgle sounds or anything unsual. Maybe I will take the shock apart and again, I have enough oil left over. What pressure do you run CC?

Sag was set to 4" awhile ago, I will check that too.
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Post by canyncarvr »

Pressure: Good grief. I've got it written down...does that help?

165# I think. It may be 145..... :hmm: Sorry.

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Post by strider80 »

awesome! Thanks CC.
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