Fork oil change

[Zigomatix]

Hi, sorry I'm sure that tis question have been asked before but my german is below zero !
I would like to know if in order to chage oil fork I have to unmount all the fork or just unscrew this bolt ? (Both side)

DSC_0137.JPG

thank you for any help.

Patrick

[scrambler]

Hi, sorry I'm sure that tis question have been asked before but my german is below zero !
I would like to know if in order to chage oil fork I have to unmount all the fork or just unscrew this bolt ? (Both side)
DSC_0137.JPG
thank you for any help.

Patrick

Hi Patrick,

yes, that's the bolt to drain the fork oil. Just push the fork a couple of times upwarts to pump out as much of the old oil as possible.

[Zigomatix]

Hi there.
I had a problem, I realise my fork was twisted. A friend of mine is currently fixing it.
I would like to chage oil type in order to limit the fork's sinking when braking. I already hardened the springs with 8 cm wedges.

Original oil is 15W.
Does anyone tried 20W ? or maybe 30W
I read that we can mix oil then 1l of 20W + 1l of 30 W = 2l of 25W (if same brand)

Any advice ?
Thx
Patrick

[scrambler]

Does anyone tried 20W ? or maybe 30W

Well I don't, the thickest oil I've tried is a 15W. You can mix different viscosities of the same brand, but I don't think a 20w or 30w will prevent fork dip.
You have already exchanged the short springs for rigid tubes, actually the suspension should now be hard enough for a driver's weight of approx. 80kg. You have to live with a certain amount of fork dip with the long suspension travel.

[Zigomatix]

OK thx Scrambler.

I don't want to prevent fork dip when braking ! just limitate it.

I am going to give a try to 20w oil. I'll let you know.
I am using my bike 100% on road so...
I now have 2 forks, one straighten out, I will leave it with 10W oil, the orther with 20W oil.

[Pit NX650]

Hi Patrick,
when adding a 8 cm wedges it won't hardends the spring but will higher up the breakthrough moment. Sounds good but reduces comfort and responsiveness.
Higher viscosity of forkoil has the same Effekt. In smaller turns it is okay for technical Tuning but a double of viscosity no more.
To reduce sinking because of the higher weight of driver and bikeload a spring with progressive and/or harder ratio is recommendable.
Wilbers and Wirth have those spring in there portfolio:
https://www.wilbers.de/shop/en/Motorcyc ... ssive.html

https://www.wilbers.de/shop/en/Motorcyc ... ssive.html

https://www.wirth-federn.de/produkt/wir ... a-u-ie-kb/
Regards
Peter

[daleipi]

'thicker' Oil in forks will result in slower rebound.

much thicker oil = very slow rebound

if the fork has to absorb multiple obstacles in quick succession it might not return to it's unloaded position until all obstacles are cleared.
in other words: if the oil is to thick the fork will stay 'short' and might become 'shorter' for as long it is constantly loaded.

[anton]

After lot's of searching and finally advised by a racing builder, did the following set-up.

ENI Fork oil SAE 10W in combination with new Wirth fork springs and spring tensioner adjustment bolts for fine tuning.

Best set-up advice ever had. Also use this set-up on my two CB500XA bikes, with oem fork springs.

[daleipi]

Good thinking!

There are TWO main things at work in a simple fork:

• Spring Load
  
  Dampening

One has pretty much nothing to do with the other, although, they overlap...

In theory the 'rebound holes' (the upper ones) in the dampening tube would have to be adjusted to the higher spring rate. No idea how.