Rear shock bump stop

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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John_S
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Rear shock bump stop

Post by John_S »

I noticed that I have no bumper on my shock shaft. In the near future I'll be servicing my shock but am torn whether to do it myself or send it off. I think if it wasn't for the nitrogen fill I would've already torn it apart. Either way at that time I'll have a new one installed. For the time being....

Is the bump stop crucial for trail riding?
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Re: Rear shock bump stop

Post by KDXGarage »

Look up some thread a couple of months ago about it.

Like most questions around here...

A few say run it in the dirt, ride hard, put up wet... Basically, the "I can't fix a sandwich" crowd.

Some will say it will be OK until you get it repaired fully.

Some will say a temporary solution, me included, of slit it lengthwise, slide it over the shaft, zip tie it.

Some will say repair fully and properly.

Welcome to kdxrider. LOL
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91 KDX 250
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Re: Rear shock bump stop

Post by 91 KDX 250 »

Ebay link of bumper stops, just add whatever size(of shock shaft diameter) in mm to the search and you should be able to find one.
Fleabay Bump Stops
Might want to get a new bladder while you're in there.

The oxygen in our atmosphere is nearly 80% nitrogen, you can buy a shock pump and just pump it up... that's what I did to my 76 cr250 shocks when I rebuilt them.
I also used transmission fluid, but these new shocks might be best to use the showa oil. Wt. of oil is up to you, it's around 2.5 to 5wt.
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Rear shock bump stop

Post by ITracerMike »

The engineer in me says that it was designed for one so it should be replaced if it has failed. Jason's method would definitely work in a pinch but If you have the time I would opt to replace the fuild in the shock and do a complete disassembly while I was at it. I recently disassembled my rear shock just to replace the bump stop and found that even though the bike has very low hours, the 14yr old rear shock oil was in need of replacement. It's not a difficult task though you will need to remove some staked material from end of the shaft with a file and have some high strength thread locker for assembly of the same nut. Like me, you may find that no local motorcycle shops do nitrogen shock charging so look in the phone book for a hydraulic shop that works on mobile or industrial equipment. They should have the proper equipment for charging your shock.
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Re: Rear shock bump stop

Post by KDXGarage »

He's on here asking for permission to keep NOT servicing it, not for help on how to properly service it. :grin:

It's a "can I keep neglecting proper maintenance without major damage" post. When it comes to members working on the shock, it rarely happens. It's just the way it is.
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John_S
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Re: Rear shock bump stop

Post by John_S »

Jason wrote:He's on here asking for permission to keep NOT servicing it, not for help on how to properly service it. :grin:

It's a "can I keep neglecting proper maintenance without major damage" post. When it comes to members working on the shock, it rarely happens. It's just the way it is.
Man did you nail that one! :bravo: Im afraid of it (the unknown of not having done one before) but I'm working up the courage. Finding a shop who'll fill the shock near me is a my biggest obstacle so far. Thank you tracermike for the suggestion. I don't want to tear it down until I know I can head somewhere the next day to fill it and be done with it. I'm going to ask a tire shop by my office that does nitrogen.
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Re: Rear shock bump stop

Post by KDXGarage »

LOL :lol:

Time, money, skill, equipment or some combo of them keeps us all from repairs we REALLY want to do ourselves. :doh:

If I were in your boat, I would buy a new bumper, slit it long ways and zip tie it back.

Rambling portion...

When you get around to rebuilding the shock, I doubt heading to the local tire place will find a lossless air chuck. Without that, don't even bother putting a puff of air in it.

To go along with what ITracerMike said,I once opened a new, but 14 year old KX shock. The oil looked bad just from oxidizing. Kayaba oil is a nice very light yellow. This was brown.

There is SO LITTLE air inside the bladder that ANY attempt to check the pressure will result in a major loss. If my memory serves me correctly, I pumped one up to 150, then checked it twice and it was down to 70.

It is my opinion that since no KDX was made in the last ten years (including South African 2007 models), ALL KDX shocks that have never had the oil changed, should have the oil changed.

One can buy a new KYB brand nut for the end of the shock shaft. No need to try to reuse a damaged nut. Do use red Loctite and torque to 25 foot-pounds of torque. Shove grease down in the shaft before hand filing or (much quicker and potentially hazardous), use a grinding wheel on a bench grinder to grind the end of the shaft flat until the peening is off the shaft end and the nut can be removed. It's not staked, but peened actually, ITracerMike. When grinding or filing the shaft end and nut off, turn the nut just a touch, then tighten and check for more filing. If you do it to soon, you will strip off some of the shaft end. YES, I did it on the first one I ever tried. OOPS! :shock: :shock:

Release all the pressure first. WEAR safety glasses. My last shock oil change, I got shock oil in my eyes even with safety glasses on! :mad:

Wear old clothes as the shock oil will leave a stain and ruin your clothes. Put a rag or similar over the bleed bolt air before removal. There can be residual pressure inside to make the oil splatter on the ceiling. YES, I have done that, too. :oops:

Whenever you get around to it, just read a good bit before digging into it.
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Re: Rear shock bump stop

Post by John_S »

Excellent information Jason!! It's going to help me and I'm sure many others who take on a shock rebuild to have some insight going in. Our eyes, clothes, ceilings, and wallets thank you! I've been checking out the parts on RMATV. I have the Race Tech oil seal, dust seal, shock shaft bushing, seal bullet, shock bumper, and a bottle of Kayaba shock oil so far added to my wish list. I'll get a new shaft nut also. I figured I would be better off with the race tech seals rather than the All Balls complete seal head based on some of your other posts Jason. Rather than spending the $40 on the seal head setting tool I'm going to take an old (size to be determined) socket and cut a straight section out so it fits around the shaft. So far that's $88 in parts including the oil, not including the shaft nut or the Race Tech 5.4 spring that I got yesterday. That was another $86 for the spring. I just finished up the 2000 KX fork swap (I removed the bladder), RB stem swap, and axle mod and after riding this weekend I really like it. I'm getting closer to diving in to the shock and then my bike will be really close to the KDX I've dreamed of having. This site and its members have been a tremendous help.
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Re: Rear shock bump stop

Post by KDXGarage »

You're welcome.

DO NOT buy the oil seal, dust seal and bushing. You would pay hell to try to undo the peening on the seal head and replace just those items. Just buy a complete seal head.

You might be able to push down the old seal head by hand. MAYBE. Since the seal head is usually replaced in the KDX shocks, you can use a hammer and punch. Who cares if you mar the top? I do have the seal head tool and it does make it so much easier, but I would skip it if I was just doing one.

Congrats on the forks!
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John_S
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Rear shock bump stop

Post by John_S »

Thank you all for the advice on the bumper. I pulled the shock, cleaned it all up with Eagle One etching mag wheel cleaner and a green scotchbrite and decided it was time for a full service. I went with a new bumper, race tech spring, seal head assembly, and KYB oil. I found a local tech/racer (right down the road) that some friends of mine use and he rebuilt it including the nitrogen charge for $75.

For the heck of it I tried disassembling the stock seal head and I see what you mean Jason. I would've torn that thing up trying to remove the bevel (or peening) to get the oil seal out. Thank you so much for suggesting NOT to just get the oil and dust seal. I haven't set the sag and ridden it yet but its a good feeling having it freshened up.
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Re: Rear shock bump stop

Post by KDXGarage »

Good job. I think once you ride it you will be surprised at how much better it feels.

You are welcome on the seal head rebuilding advice. The steel ones are a nightmare and not worth it.

EDIT ADD-ON: If it didn't happen, the piston band and o-ring should have been replaced while he had it open. If you do it as the next oil change, it can be swapped without taking the nut off the shaft.
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