KDX 420 rear shock

Discussion specific to the various air-cooled KDX models sold in the USA
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IanD
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KDX 420 rear shock

Post by IanD »

Hi
I need to replace or restore my rear shock. Have seen one for a 450 and it has a remote reservoir otherwise it looks identical to the 420 one. Does anyone know if there are other differences ?.
Thanks in advance
Ian
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KDXGarage
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Re: KDX 420 rear shock

Post by KDXGarage »

Welcome to kdxrider.net. Thanks for joining and participating.

Based on the pic below, it looks like it is serviceable. If it has the two pin holes in the cap and a place to put nitrogen, one can usually service it / have it serviced.

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IanD
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Re: KDX 420 rear shock

Post by IanD »

I sent my shock off for rebuild however the shaft needs re-chroming and they are struggling to remove the clevis from the shaft. Do you know if this is possible ?.
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Re: KDX 420 rear shock

Post by KDXGarage »

Sorry, but I do not know. I have never worked on a KDX420 shock before.
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IanD
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Re: KDX 420 rear shock

Post by IanD »

Just FYI, I have had a look and the clevis is threaded onto the shaft. The workshop have tried heating it up but are struggling to break the seal on the threads of the shaft/clevis as it is difficult to grip the shaft whilst turning the clevis. I suggested heating up with oxy/acet rather than just a blowtorch to help. Will keep you informed of progress.
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Re: KDX 420 rear shock

Post by KDXGarage »

I think that a set of properly sized shaft holding blocks are needed.

Good luck.

Thanks for the info on the clevis.
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81KDX420rider
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Re: KDX 420 rear shock

Post by 81KDX420rider »

Any luck with this, I have one to do also?
IanD
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Re: KDX 420 rear shock

Post by IanD »

Still no luck removing the fork, I have fitted 450 shock now. Just needed a bracket for the remote res.
81KDX420rider
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Re: KDX 420 rear shock

Post by 81KDX420rider »

I had Shockaholic in NY rebiuld my forks and shock, my orginal shock was pretty bad but I found a KX250 shock that was rebiudable and the bonus is it has a remote resevior and rebound adjustment.
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Re: KDX 420 rear shock

Post by whocares191 »

reviving this old thread as I picked up a 1981 kdx420 for $350 and am building it to a kx420 for the track. The shock as far as i know is near impossible to rebuild and if it does get rebuilt it wont be very good. I spent a good amount of time on the phone with racetech and they built one of their custom shocks for an early 80s kx and it took quite a while to get the spring on. The unitrack at the time was super innovative but unfortunately they decided to have a falling rate and you need a spring from a semi truck. It's really hard on everything but I still plan on not changing the rocker arm and having the shock made to keep the bike semi original. The forks however are easily replaceable and rebuildable, i'm going to start a build thread on this kdx/kx420 I have since there will be a lot to do. There must be 5lbs of gussets and plugs i plan to add to the frame so it doesn't break on me. Specifically by the front motor mounts, I almost want to cut the whole downtube off and put a thicker one on with a slight bend, its just plain DOM steel tubing.
Current Bikes:
2004 kdx220r for trail riding
2001 kx250 for track riding
1990 kx500 for dust collection
1981 kx420 for vintage races
2021 KLX110L for my first 4 stroke :naughty:
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