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Discussion Starter #1
Hi there fellas,
here is my problem.Local mechanic say and my friend say i dont need to as long as seals are fine...but the articles on google say its recommended to change every 1 or 2 years.
i got 2014 duke 390 which is at 28k kms and the seals are okey.the bike is second hand by the way..
i bought the fork repair kit ( 4 seals + 2 bushings ) and motorex 4w fork oil...
my question is should i change the seals and oil or should i wait till the seals are broken?
Thanks...cheers
 

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should i change the seals and oil or should i wait till the seals are broken?
Interesting fork. Totally different than the 2017 forward.

What I usually do is pull away the dust wiper, then take a dull edge pocket screwdriver (or a seal spoon) and test the resiliency of the primary seal edge hidden beneath the wiper.

If there is no seepage and the seals are supple and there is no bushing play in the fork tube, it's not a dirt bike, I forego breaking it all the way down.
I just invert it and pump all the oil out, with the upper cap unscrewed... making sure to be emptying into (in this case, a clean 500 ml measure cup). Now take a look at the sediments that may have come out with the old oil, and reevaluate if necessary your current stance on how far to go.
If you are worried there might actually be bushing wear, if the teflon coating has likely worn off the bushings, by all means, tear all the way down!

If you thought the fork shoulda' been more progressive, stiffness, braking to the corner, add another 10cc to what you drained out and refill it with that amount of new oil. Why? because it will cause the trapped-air spring pressure to ramp up slightly faster.

According to what I'm reading in the serv manual, each leg holds 440ml.

Did you already see in the manual how this thing comes apart internally?

Do you have the required tools if you decide to tear all the way down?

Can I stop talking now, because I feel like I've got a monkey on my back again.
[Oh dear god, someone make him STOP!]
 

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Discussion Starter #3
Nah you spoke well 😂 let the monkey talk more.i have checked the repair manual and it says 4400ml of fork oil is recommended each leg
 

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If the seals aren't leaking, leave them be.
Change the oil. It's easy and suspension oil degrades over time and use, just like engine oil. You'll see how disgusting it is once you drain it :D
You can change the oil without touching the seals, you don't have to tear everything down:

  • remove wheel, fender and brake caliper
  • loosen the top triple clamp bolt
  • loosen, but not unscrew, the top cap (24mm wrench afair) - do not loosen or tighten the top cap if the top triple clamp bolt is tight
  • loosen the lower triple clamp bolts
  • slide leg out
  • unscrew top cap, it should be loose now and easy to do without vice grips
  • slide the upper tube of the suspension down a couple centimetres, you'll see the fork internals but you don't need to touch them
  • tilt the whole thing to the side and drain the oil into a bucket
  • measure how many millilitres came out
  • pour in the same amount of fresh oil
  • slide the upper tube back up, screw the top cap in finger-tight
  • slide the leg back in, measure it's the same height as the other leg
  • tighten the lower triple clamp bolts (consult manual for torque, afair around 12nm?)
  • tighten the top cap (only light pressure needed, the top triple clamp bolt will act as a pinch bolt anyway)
  • tighten the top triple clamp bolt (again, small torque, like 15nm?)
  • repeat for other leg
  • reinstall wheel, fender and caliper
 
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