3. Front forks: dismantling

  1. Always dismantle fork legs separately to avoid the risk of interchanging parts and causing increased wear. Store all components in separate, clearly-marked containers and work on one leg at a time to ensure this.
  2. Holding the top plug with an open-ended spanner, remove the filler plug then unscrew the drain plug and hold the leg over a suitable container to drain the oil. Pump the leg vigorously to expel as much oil as possible.
  3. Using the wheel spindle placed in one of its lugs to prevent rotation, unscrew the damper rod Allen screw from the base of the fork lower leg.
  4. Clamp the fork lower leg by the caliper mounting or wheel spindle lugs in a vice equipped with soft jaws to avoid marking the soft alloy, then use a suitable rod to press in the top plug until the retaining circlip is exposed. Push the circlip down into the leg on one side only so that it can be gripped with a pair of pliers and withdrawn. Allow the spring pressure to push the top plug out of the stanchion; in some cases the sealing 0-ring may be such a tight fit that the top plug must be extracted using a pair of pliers to grip a bolt screwed into the filler plug thread.
  5. Make a very careful note of the order components are removed, and which way round each is fitted. Note that any references to K75 S suspension components automatically apply to any model fitted with S type suspension.
  6. On all models except the K75 S, remove first the white nylon spacer then the fork spring, noting which way round the spring was fitted, also the spring seat at each end.
  7. On K75 S models remove the spacer(s), followed by the top spring, then the main spring; note carefully which way round each component was fitted.
  8. On all models, remove the damper rod Allen screw and pull the fork stanchion assembly out of the lower leg. Owners should note that the rebuilding procedure is quite difficult if the damper components are removed from the stanchion; it is recommended that these components are left undisturbed unless their removal is absolutely necessary,
  9. Remove the circlip from the stanchion lower end and note the number and thickness of shims fitted above it. Pull the damper assembly carefully out of the stanchion; as the damper piston emerges note which way round the piston ring is fitted. The valve housing can be removed from the lower end of the damper rod and the piston ring can be removed from its groove.
  10. If the damper components are to be dismantled, thoroughly clean the rod assembly, removing all traces of oil and dirt and finishing off with a rinse in hot soapy water to remove any flammable solvents. On K75 S models measure the exact overall length of each damper rod from the piston top surface to the rod lower end and record the results. The damper piston is screwed on to the rod upper end and secured at a precise distance by Loctite 638 or 273 thread-locking compound; to release this it must be heated in a gentle flame until the Loctite starts to burn (approximately 250°C/482°F), whereupon the piston can be gripped with a pair of pliers or similar and unscrewed. The damper components can then be removed alter taking careful note of exactly which way round each is fitted.
  11. To remove the fork oil seals, withdraw the dust excluder from the top of each fork lower leg and carefully lever out the seal. Use only a tool with well-rounded edges to avoid scratching the seal housing and place a piece of wood across the top of the leg to act as a pivot and prevent damage to the leg itself. If a seal is very difficult to remove, pour boiling water over its upper end, taking care to prevent the risk of personal injury.
  12. On K75 S models once the seals are removed the spacers can be tipped out of the fork lower legs; note which way round each is fitted.


Fig. 7.1 Front forks


3.4a Push top plug. into stanchion until circlip can be withdrawn ...


3.4b ... top plug should be pushed out by spring pressure but may require pulling, as shown, if 0-ring is a tight fit


3.9 If damper rod is removed from stanchion, note number and thickness of shims


3.1Oa Do not dismantle damper rod unless necessary - piston must be heated to release locking compound ...


3.1Ob ... Note carefully which way round components are fitted before removing them