For your forks to ride smoothly with out bottoming or topping out you must install the slippery JS Turcite bushings along with the aluminum sleeves. Turcite is the best material available for fork bushings and will easily outlast Teflon. For the aluminum sleeves, plug the 1/8” diameter oil escape hole in the bottom of the fork tube (just above the lower bushing) or you will not get the necessary oil cushion to prevent “top out”. Thread the 1/8” hole with a 6-32 tap and use the provided set screws (coat the threads with red loctite to keep them in place). Make sure the set screws are not proud of the surface or installed too deeply. For details on the aluminum sleeves (see damping sleeves).
Replace your worn aluminum damper caps with tight fitting JSM Ampco 15 bronze caps for longer life and improved reliability. The damper rod shaft should measure .375″. The steel valve cups are also a tighter fit.see damping upgrade video
If you have damping tubes with holes below the conical section then you need to cover those holes with JS alum sleeves to achieve a hydraulic bump stop and avoid bottoming “clunk”. Then you can drill only one 1/8″ hole in the middle of the conical section as in the photo below if you want a little compression damping. The value in compression damping is reducing front brake dive and bottoming in racing – but you will feel more bumps. You can go down to one 3/32″ hole minimum for increased compression damping when racing. 1/16″ is too small and will cause cavitation. But an increase in compression damping gives you a harsher ride and is not recommended for the street. One or two 1/4″ holes in or above the conical section will give the smoothest ride with little or no compression damping.
Place the Oring on the bottom of the damper tube. You must have the aluminum washer installed in the bottom of the slider to avoid crushing the Oring.
To prevent leaks at the drains, install the small Oring on the drain screw with the small aluminum ring. Dominators and other early Nortons may need to change to Commando fork drain screws to accept the small Oring.
Use 5 oz of 15 weight fork oil in each leg. Do not use “leak proof” seals which have too much stiction. Now you’ve got oil tight, modernized, stickion free forks with excellent damping.