Shock Bottom Out Bumper Install 99 400F

I have a 99 YZ400F with a blown out bottoming bumper on the rear shock. I have the shock off the bike with the spring removed but do not know where to go from here. Do I have to send this to a suspension shop or can it be installed without tearing into the hydraulics? I have searched through the forum and my Clymer manual and can't find anything about it. This job doesn't look easy now as I thought it would be. Thanks for any help or suggestions.


You will have to remove the shaft from the body, grind down the peening holding the nut on the top of the shaft, remove the nut, valve and shim stack, seal head assembly, and finally the bottom-out bumper. Install in reverse order and use Locktite on the nut. You will then have to follow the proper procedure to refill and recharge the shock with Nitrogen. It's kinda complicated but doable.

Thanks for the help SXP. Since it is a 99 model, I might as well just have the shock rebuilt and revalved too while I am it. I usually do all of my own work but I think I will leave this one job to the pros with the experience. Thanks once again.


The job is not that difficult. Read the MX tech instructions first and you will haver no trouble. Think of the money you will save down the line on shock oil replacements.

I found myself in the same situation two years ago. They guys here talked me through the job. I have since completly rebuilt the shock and changed the oil twice. My total out of pocket cost has been under 25 bucks for oil and a few parts.

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