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The O-ring around the manual tensioner bolt on Honda CX500s and GL500s can leak a surprising amount of oil once it stops working properly; here's how to change it. Please note that due to the design of the bolt you cannot remove it far enough to access the O-ring while the rear engine cover is still on the block, meaning that you need to remove the motor to get access to that little O-ring. Because of this - and the fact that it should cost under a dollar for an O-ring of that size from a bearing shop - it's often recommended that you change it as a matter of course when you have the engine out to do other work if it hasn't been changed as far as you know. You can remove the old O-ring easily with a pick or similar tool:

The O-ring - 6.5mm x 3.1mm - is part number 91312-415-000 (eBay US, eBay CA
, eBay UK
, eBay AU
) for all of the manually-adjusted models - most CX500s and GL500s around the world.

Clean up the bolt and the recess that the O-ring sits in then slide it over the end of the bolt:


All done. If you are doing this as part of a triple or quadruple bypass click here to go back to the main page.
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