Re: Fork Seals

Posted by sgtslag on May 04, 2012; 3:36am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Fork-Seals-tp3960436p3961143.html

Dexron III is specified for 1979 CB750K's, but the current, Dexron IV/V will work, as it is backwards compatible, just like it is in cars.  The key to fork hydraulic fluid is that it remain absolutely stable in viscosity, which is uber-critical for transmission fluid, as well.  Fork Oil is very highly refined oil, uber-stable in viscosity, and uber-expensive, around $15 per quart, available in various viscosities (typically 5-20).  Dexron IV/V Automatic Transmission Fluid is available everywhere, for an average price of $4 per quart.

Fork Oil/ATF wears out, from repeated abuse suffered within the forks.  It is recommended that it be replaced every two years -- nothing lasts forever.

The various viscosities of Fork Oil give different stiffness levels, on the forks' compression rates while riding.  Some folks like it hard, some like it soft.  Typically, the heavier the viscosity (15, 20), the stiffer the response.  The lower the viscosity (5, 7, 10), the softer the response to bumps, by the fork tubes.  The actual viscosity of Dexron ATF is allegedly around 8.

Fork Gators will prevent bug remains (chiton shell material) from sticking in the fork tubes.  This chiton is razor sharp, and it cuts up the fork seals, causing them to eventually leak ATF/Fork Oil.  Adding Fork Gators (even if your bike wasn't equipped with them), will double the life of your fork seals.  At least, that is the theory, which is generally accepted.  Cheers!