675.cc • Triumph 675 Forum

Ohlins fork oil and seal change

Discussion in 'Maintenance & Tweaks' started by wobblybiker99, May 26, 2023 at 12:05 AM.

  1. wobblybiker99


    Thread Starter

    Had a very slight leaking seal, mainly when the bike isn't used much, but the oil hasn't been changed for 10yrs and 25k miles so this job is well overdue.
    Please don't take this as a "how to" as I'm no expert and its my first time working on forks, apart from an oil change on the Thruxton's Showa BPF forks the week before.
    Its all in the Triumph workshop manual anyway.
    Wheel off and forks out with no drama, remembering to crack the fork cap first, the fork top cap loosened fairly easily with the pin wrench after releasing the top yoke.
    top cap unscrewed, there's no spring pressure at this stage. 20230523_105810.jpg

    Then hold the top cap and slacken the locknut, both 17mm but a standard (mine anyway) open ended spanner wouldn't reach the nut so had to use an adjustable which had longer jaws, luckily its not massively tight, the plastic bag is to protect the top cap.

    20230523_105826.jpg 20230523_110131.jpg

    Then hold the damping rod and unscrew the nut to release the spring, deep socket was useful for this, the reverse of this stage is the only tricky bit in the process.


    Then you can remove the spring, spring spacer and adjustment rod and pour out the oil, remembering to catch the damping needle and spring, or fish them out the oil with a magnet.
    Then you can separate the inner and outer tubes and clean everything, a full stripdown would include removing the cartridge but that needs more specialist tools and wasn't necessary for this job.

    Oil was a bit manky as we say up ere, not sure if the Ohlins oil is coloured originally or supposed to be clear.

    Can see how bad it was around the seal area, seal removed ok, warmed the outer tube gently with a blowtorch first as I don't have a heat gun but would have probably come out regardless.


    everything apart, hope i can remember how it goes back together:confused:
    No wear showing, plating in great condition.

    20230523_112323.jpg 20230523_115719.jpg

    Used Ktech supplied oil seals which I think are Ngk, dust seals were ok so cleaned and reused.
    Went for Motul 5w as from the viscosity charts I've seen and other peoples recommendations its supposed to be the nearest equivalent to the original Ohlins fork oil
    Filled with 0.5l then level set to 150mm below top tube with my homemade oil extractor, just sucking on a tube, then a good while moving the damping rod up and down until all the air is purged.
    Didn't take any pictures of re-assembly, basically the reverse process, the only tricky bit is holding the damper rod up while you drop the spring in, there is a triumph tool for this but most people just use a piece of wire around the thread, then grip the rod with long nose pliers through the spring while you fit the top spring seat and hopefully have a couple of threads showing to start the nut.
    Ready to go back, bit of red rubber grease on the O ring.


    Back in the bike, initially thought the forks had been set incorrectly originally but then re-read the manual and realised the fork pull through is 12mm to the top of the outer tube and not the top cap of the fork, not before I'd tightened the forks and put the wheel back though:rolleyes:
    Would normally use the clip ons to hang the calipers and not the indicators but awkward when removing the forks, made sure the weight was right on the inside though.

    Will update later regarding how they feel as the test ride didn't go quite to plan.:(
    Last edited: May 26, 2023 at 12:16 AM
    • Like Like x 2
    • Thanks Thanks x 1
  2. StMarks

    StMarks PTG

    Location: HU15 2DS
    Another excellent task accomplished with your usual proficiency.
    I do wish I could manage to work as tidily as you.
    • Thanks Thanks x 1
  3. wobblybiker99


    Thread Starter

    you didn't see the state of the garage after, seemed to use twice as many tools as expected plus multiple bits of wood to block up the fork leg and oily containers everywhere, still need to clean out my mums measuring jug I used on the Thruxton forks, will probably end up keeping it though.:D

    After refitting the forks they initially felt very soft in compression and rebound just bouncing the bike by hand, so much that I was questioning if I'd done everything correctly or chose the wrong grade fork oil, I was sure I had the level right and although I didn't fill them by volume judging by how much came out I'd put at least the same (if not slightly more) back in.

    Had to wind the adjusters all the way in to the Track setting to get enough damping, which is way harder than my normal setting.
    Left the bike overnight and set off on my test ride next day, with Allen key to make any adjustments, straight away the forks felt way too hard as I would expect on "track" settings (Reb 7 Comp 10), I'm guessing that either overnight or just with riding the bike the forks have "settled in" or purged some remaining air and are now back to their normal operating range, rather than the very soft feel when first built up.
    Ended up with the damping back somewhere near my normal setting, Reb 12 Comp 20, which makes me more confident that I haven't messed up, and more importantly no leaks.
    Never comment on general handling or cornering as on whatever setting the bike is way better than I'll ever be, just usually set them to cope with our atrocious bumpy roads and hard braking.
    Also I'm switching daily between two very different bikes, both of which I've just reset the headstock bearings and changed fork oil so that complicates things a little.
    Still got some tweaking to do but much happier knowing they're operating in their "normal" range again

    Test ride was interrupted when the bike failed to start and had to get recovered after stopping to make some adjustments, unrelated to me working on the bike the day before it turned out.:(
    Will make a separate post
    Last edited: May 26, 2023 at 9:57 AM
    • Funny Funny x 1
  4. SW73


    Location: Sunderland
    Great work. I've a fork oil change myself to do. Hmmm. We shall see...but I've a workshop manual and plenty of my girlfriends er jugs to decant the fluid into! I'll let you know how I get on. Always satisfying when it's sorted...but like you...the tool situation nds up as carnage!
    • Friendly Friendly x 1
  5. Nik


    Location: Holland
    Job well done indeed,where would we be without a black and decker workmate??
    Answers on a post card to ….

Share This Page

  1. By using this website you agree to our Cookies usage. We and our partners operate globally and use cookies, including for analytics, personalisation, ads and Newsletters:
    Dismiss Notice