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ASK THE MXPERTS: The Plastic Tube Inside My YZ450F Kayaba Forks Split Wide Open; This Happened Twice; What Is The Fix?
   ASK THE MXPERTS:
THE PLASTIC TUBE IN MY YZ450F KAYABA FORKS SPLIT WIDE OPEN; TWICE; HELP ME FIND A FIX
This is a fairly common Kayaba failure.

Dear MXA,
    The other day I was working on my brother’s YZ450F forks and I discovered that his plastic compression piston (what Yamaha calls the base valve) was cracked (I enclosed a photo). We had to buy a new one and it was expensive. Yesterday I was doing seals on my bike and the the same thing is wrong with mine. What is the cause of this and what can I do to prevent it from happening again?

    There are problems with every unit. Unlike on Showa forks, Kayaba puts an O-ring seals at the top and bottom of the plastic chamber. Pressure builds up inside the plastic tube as it heats up and it splits (as you have seen). The solution, and it is a very simple solution, is to drill a 1/16-inch hole in the center of the plastic tube to relieve pressure. This is a quick and easy fix that causes no problems. We checked with Bones Bacon at Pro Circuit and he says they do this on every Kayaba fork. Pro Circuit will sell the plastic tubes to riders who have broken theirs. www.procircuit.com
 

The very small hole in the center of the plastic tube is the fix.

   You can send your questions or comments to mxa@hi-torque.com




MAY 2012, VOLUME 40, NUMBER 5
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