Fork Oil Change

[teecee90]

I decided to change the fork oil today. Followed the instructions in the Haynes manual, which says to measure and note the position of the spring spacer retaining nut. How critical is it to get this right and should both sides be the same? I measured the distance as 11.6 mm on the right side and 14.6 mm on the left side. I was expecting them to be the same or very similar.

[AyJay]

It's very important. The handling is destroyed if the forks aren't set up identically. Not quite the same thing, but I once rebuilt mine and I was in a hurry to get down to the dealers and pick up some parts so hadn't reset the compression and rebound and jeezuz, hitting bumps mid corner kicked the bike way out of line. Really dangerous....

[sadlonelygit]

Pretty sure that for most of my spannering career we often used different rate springs in the forks to get the ideal set up. It IS important to set the rebound damper rod datum point identically in each fork, which iirc is 11mm of thread above the nut.

[AyJay]

Yes sadlonelygit, agreed, and I know that many of Yamaha and other manufacturer's bikes even have the rebound in one fork and compression in the other so there are different configurations that work, but on this bike, they're supposed to be a matched pair. I would not want to ride with different amounts of oil and air gaps given what I experienced with different rebound and compression settings.


Having said all that, when a fork seal goes, you get the same effect. But that's an MOT failure, and not just because you might get oil on the brakes.

[teecee90]

All done and dusted - thanks for the advice. Was a relatively simple job just to change the oil. Each fork took about 410-420 ml to reach to 140mm fill level. I'll probably fully strip them, change the seals and check the bushes when I do it again.