Motorcycle Shock Shaft & Piston Lock Nuts

Right in the centre of your motorbike's coilover is the main damping shaft. At the top end it holds the piston inside the shock absorber body while at the bottom end it screws onto the Clevis or Yoke. A clevis has a split fork of two tabs with a gap between them (like the diagram shown), while a yoke has just one wide ring sticking down (much like the top of a shock body).

These top locknuts are used on the smaller internal end of the shock shaft for securing the valving piston assembly - the complex oil-flowing piston with it's matching compression & rebound shim stacks. You can't use a normal nut due to the constant vibration, and you can't use loctite or nylocs either, due to the heat & oil. You need a special fujilok lock nut (or OEM equivalent) with a locking stainless steel spring insert. Read our nuts & bolts tech article to become a fasteners expert.

If your motorcycle rear shocks are rebuildable (not all of them are) and you're not happy with the way the suspension acts, you can service the internals, getting the components back to OEM factory spec. If you also have comp & reb adjusters you should read our DIY damping adjustment guide so you can adjust the clickers to better suit your riding - but if it still isn't perfect there is one more step you can take - revalve the damper rod piston. Revalving takes a lot of testing to get right so we recommend it only for professional workshops - get a better idea by watching our expert Nick tune a Yamaha WR250R Shock.