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Changing fork springs and fork oil

captainscarlet

By captainscarlet
in FJ-09 Tech Tips/How to's

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captainscarlet

captainscarlet

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This is a walkthrough of the steps I took for changing the fork springs and oil on my 2015 Tracer.  There are numerous how-to's around and many others have done this before me.  I performed the job more or less exactly as Dave Moss does in this video:

In my case I didn't need to separate the fork leg tubes as I wasn't changing the seals.  I also ignored the part about the compression circuit as our bikes are not so equipped.  Otherwise the above video is a great guide.

Tools

I did buy a couple of tools as follows.  The cost of these was modest and certainly considerably less than a dealer would charge for actually performing the work.

If you don't won't to purchase these tools there are also numerous YouTube videos showing how to make your own versions of the above. 

Walkthrough

  1. Bike on centre stand
  2. Raise the front of the bike.  This needs to be done without the use of the forks as they are coming off the bike.  I used a triple tree stand.
  3. Remove the front brake calipers, two bolts on each caliper and hang them out of the way with bungee cords/wire.
  4. Remove the front wheel.  Loosen the pinch bolt on the bottom of the right fork leg and unscrew the axle using a 14 mm hex.  Tap/pull the axle out and note the spacer on the left hand side.  Hang the ABS sensor assembly out of the way.
  5. Remove the front mud guard.  Undo four bolts on each side and open the brake line holders and pull the brake lines free.  As you remove the mud guard retrieve the four silver collars that sit on the inside of the mud guard.
  6. Remove each fork leg one at a time; these instruction are for the right fork leg which contains rebound damping.
  7. Loosen the pinch bolt on the upper triple tree.
  8. At the top of the forks use a well fitting six sided socket to crack the fork cap open slightly.
  9. Loosen the pinch bolts on the lower triple tree and carefully remove the fork.  You may meet some resistance but just rotate gently backwards and forwards and it should slide out
  10. Secure the fork leg upright in a vice (watch the beginning of the Dave Moss video for some advice on this).  I also had a wooden stool underneath the bottom of the fork leg which the fork leg was standing on.
  11. Back out the preload and rebound adjusters so they are fully out.  Write down what settings you had before you do this.
  12. Unscrew the fork cap and loosen the vice jaws slightly so the outer tube can drop down revealing the fork cap and plastic spring spacer.  Once the outer tube is all the way down snug up the vice again.
  13. Use your spring compressor to compress the spring so that you can get at the lock nut under the fork cap.  The two bolts on the spring compressor screw into the two holes on the side of the plastic spring spacer.  I then used a ratchet strapped hooked onto each side of the spring compressor and looped around the bottom of the fork leg to compress the spring.  Once the spring was compressed sufficiently I lifted the fork cap to expose the lock nut.  At this point I inserted my damper rod holding tool between the lock nut and the spring spacer.
  14. Remove the fork cap by cracking loose the lock nut underneath as you hold the fork cap with an appropriate spanner.  Unscrew the fork cap and set it aside.
  15. Remove the damper rod holding tool from under the lock nut and carefully loosen the ratchet strap relieving tension on the spring.
  16. Lift the plastic spring spacer off the spring and set it aside.
  17. Lift the spring out of the fork tube; have a rag handy as it will be covered in oil.  If you're fitting new springs chuck the OEM spring in the bin! 😋
  18. Lift out the damper rod from the damper tube and set it aside.
  19. Drain the oil. Undo the vice and, holding the bottom of the fork leg/brake caliper mount, carefully tip up the fork and pour out the old oil into a suitable container.  I put the tube upside down back in the vice and let it drain for a while.  It's also a good idea to pull the damper tube in and out a few times to help get all the oil out.
  20. Fill the fork with new oil.  Put the fork back in the vice the right way up and with the outer tube all the way down.  Make sure the fork is vertical.  Carefully pour in your oil of choice.  Don't worry too much about volume, it's the height of the oil or rather the air gap at the top that we're going to measure.  Pour enough oil in so that it's fairly full.
  21. Bleed the fork.  Put the damper rod back in the damper tube and attach your fork bleeding tool to the top of the damper tube.  Now pull the damper tube up and down around 10 times or so to get all the air out.
  22. Check the height of the oil.  I had an old syringe to which I attached a thin solid tube of the right length.  I used this to suck oil out of the fork so that the correct height was achieved.  The service manual calls for an air gap of 174-175 mm.  Advice on this board suggested that a good gap is suspension travel plus 25 mm.  For the Tracer that is 137 mm + 25 mm giving 162 mm.  I settled on 160 mm.
  23. Reassemble.  Put the damper bleeding tool back on so you don't "lose" the damper tube down inside the fork.  Carefully slide your new spring into the fork tube being careful not to spill any oil.  Slide the spring spacer over the top.
  24. Re-compress the spring and insert the damper rod holding tool between the spring spacer and the lock nut.
  25. Re-attach the fork cap.  Make sure the rebound adjuster is wound all the way out i.e. anti-clockwise.   Then wind in the adjuster the maximum number of clicks specified in the manual, in my case 11 clicks.  Screw the fork cap back onto the adjuster rod until it stops.  Tighten up the lock nut against the base of the cap and snug with a spanner.  Remove the damper rod holding tool.
  26. Carefully slacken the ratchet straps and ensure that the plastic spacer engages properly with the fork cap. Once this is done the fork spring compressor can be removed.
  27. Loosen the jaws on the vice slightly and slide the outer tube up to the threads on the fork cap.  Rotate the cap anti-clockwise first until you hear a click, then wind clockwise to screw the cap in.
  28. Hold the fork in the vice again and snug up the fork cap with an appropriate socket/spanner.
  29. Slide the fork leg carefully back into the triple trees.  I used a bit of WD-40 to lubricate the upper part of the fork leg to help it slide into position.
  30. Set the fork leg at the correct height. Factory is with the top of the fork leg flush with the top of the upper triple tree.  Snug up the upper pinch bolt.
  31. Repeat the above steps with the left fork leg.  This is slightly easier as there is no damping rod to worry about.
  32. Refit the mudguard and attach the four bolts loosely.  Re-clip all the brake lines in the correct position 
  33. Refit the wheel taking care of the spacer on the left and the ABS sensor on the right.  Do not fully tighten the axle.
  34. Refit the brake calipers and loosely tighten the brake caliper bolts.
  35. With the bike on the centre stand/paddock stand remove the front triple tree stand.
  36. Stand on the foot pegs and using your hands and body weight push vertically down on the centre of the steering stem a few times.  This allows everything to line up.
  37. Tighten up the pinch bolts on the lower triple tree and then the front axle, pinch bolt, mudguard bolts and brake caliper bolts to the appropriate torque.
  38. Slacken off the pinch bolts on the upper triple tree and then tighten the fork caps to the appropriate torque, re-tighten the pinch bolts. 
  39. Take the bike off it's stands and set rider sag and initial rebound.

Job done!

CS

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captainscarlet

captainscarlet

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Today I dialled in the preload and rebound in the garage.  I made 3 videos to illustrate the effects of different rebound settings:

  1. Too little rebound, adjuster all the way out
  2. Too much rebound, adjuster all the way in.
  3. Rebound just right, adjuster in the middle of its range.

You can see in the first video that the forks bounce back very quickly, past the rest point before settling.  In the second video the rate of return is very slow in the latter half of the forks travel.  The third video shows a swift and steady rate return to rest, without bouncing.

CS

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