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  fork rebuilds Lnav
   4CS fork - setting oil level  
  • Click on picture to enlarge.
  • Quick description on setting oil level
    1. Drop outer aluminum tube until dust seal bottoms against lug. 
      • Notice bleed holes in chrome tube toward the top.
    2. Fill with fluid to top of chrome tube.
    3. Stroke outer tube to allow fluid to flow thru chrome tube bleed holes. 
      • This fills area between inner and outer tube with fluid.
    4. Set oil level.
    5. Pull outer tube up until top of (8mm) ctg rod is flush with bottom of outer tube threads. 
      • This raises oil level.
    6. Drop outer tube and reset oil level.
    7. --> Our method starts with oil between the inner and outer tube.  If you have no oil in the gap, your oil level will drop by 16mm as fluid fills the space.  (see below).
    8. --> NOTE THAT KTM recommended oil levels are with "no oil between inner/outer tube"  (see below).


Drop outer aluminum tube.  Notice bleed holes in chrome tube.


Fill fluid to top of chrome tube.  Notice air bubbles as fluid fills space between inner and out tube.


Oil level drops as the gap is filled.


Pull outer tub up a few inches to speed up the gap filling process.  You can hear the fluid being forces into gap between inner and outer tube.


Drop outer tube and set oil level.


Visually notice the oil level.


Pull the outer tube up until the top of ctg rod is even with the bottom of aluminum threads.

This forces excess fluid in the gap back to center of tube.


Drop outer tube.  Notice the oil level has risen.  The oil level always increases 16mm.


Reset oil level.  Now the level is correct.

NOTE!! If you are setting a high oil level (e.g 65mm), you may need to repeat steps 7-8-9 a second time to ensure that no excess fluid makes it way back thru the bleed holes into the gap.

We have just set the oil level "with oil between inner/outer tube".

On the spec sheet, we refer to this as:
"with oil betwn in/out tube"
- or -
"pull tube up"

    10)  The method described above is different than called for on the KTM spec sheet, and will yield different oil levels!!  (10mm difference)

  • Notice the KTM spec sheet calls for (no oil betw.inner/outer tube).
  • 65mm using KTM's method with "no oil betw.inner/outer tube" = 75mm using our method
    "with oil betw.inner/outer tube".


The KTM "no oil " method will only work when you disassemble the fork and replace fork seals.  At this point, there is no oil between inner/outer tube.

  • Once you ride the bike, there will always be oil between the inner/outer tube.  If you want to change oil level or replace fork springs, it is difficult to remove oil from between the tubes.  THEREFORE, we always use the "with oil" method and fill the gap with fluid before setting oil level (as described above).
  • With the KTM method, when fluid transfers from the gap to the center of the tube, the oil level will drop 10mm.
  • If the KTM spec sheet calls for 65mm, set the level at 75mm using the "with oil" method.
  • If the KTM spec sheet calls for 100mm, set the level at 110mm if using the "with oil " method as described above.
Untitled Document Untitled Document
 fork rebuilds rnav
4CS fork kit installation
4CS kit install instructions
4CS kit tools
4CS fork - fill ctg tube
4CS fork - setting oil level
4CS fork - spring preload
4CS kit explaination