Time for new fork oil and seals, some advice needed.

Hi all,

I'm having the fork oil and seals replaced on my k9 1250 by a mate. I've never done forks before.

Any ideas from those in the know what weight oil I should use? Was thinking of changing the springs aswell.

I'm 100kg with riding gear on if that helps.

I don't want to spend big just improve things a bit.

Cheers Badger

I always use 15w

Everyone will have a different suggestion but for what it is worth.
If you are going to change springs then go for 0.95kg/mm springs for your weight. You could most likely get away with as low as 0.85kg/mm springs quite easily also. It will depend on what you are after in the front end (do you ride hard and want a race bike type of handling or are you after a more planted and secure front end that still rides the uneven crap roads well) IMO go for linear rate not progressive but it's a personal thing. The bandit has progressive from factory at about .7kg/mm from memory
If you are not going to change any valving in the forks then go with 7.5w oil (this will depend on which oil brand you use but my suggestion is based on using motul fork oil) and 5mm more air gap as a starting point.

Thanks for the info dhula,

I'm after a more secure and planted front end.
I'm no racer so don't need a sports style setup, but I like to have a bit of fun.
5mm air gap? does that mean using a spacer or less oil. I really hope thats not a dumb question.

Kaupy

Are you using 15w oil with the standard springs and valves and how much difference was there?


Cheers, badger.

5mm air gap? does that mean using a spacer or less oil.

Less oil

Are the springs easy to source?

Badger wrote:Thanks for the info dhula,

I'm after a more secure and planted front end.
I'm no racer so don't need a sports style setup, but I like to have a bit of fun.
5mm air gap? does that mean using a spacer or less oil. I really hope thats not a dumb question.

Kaupy

Are you using 15w oil with the standard springs and valves and how much difference was there?


Cheers, badger.

Sorry dude. I haven't done the forks on the bandit yet. I've only done fork seals and oil changes on hondas, a kwaka and a couple of yammys for other people. But i've always used 15w oil in them and had good reports from the riders.

There are a lot of variables to take into account. I had my forks done not so long ago, new gold valves and racetech springs. The expert that did the work replaced the oil with 5wt. I thought that that sounded a bit light, but he is the " expert ", and hey, they feel Fan-bloody-tastic. I would suggest revalving at the same time as doing the springs.

Hammy wrote:There are a lot of variables to take into account. I had my forks done not so long ago, new gold valves and racetech springs. The expert that did the work replaced the oil with 5wt. I thought that that sounded a bit light, but he is the " expert ", and hey, they feel Fan-bloody-tastic. I would suggest revalving at the same time as doing the springs.

No expert here, but i reckon the lighter oil will flow thru valves at the correct speed. Unlike a heavier oil. I may be wrong though.

Boatz wrote:
i reckon the lighter oil will flow thru valves at the correct speed. Unlike a heavier oil. I may be wrong though.

You are correct in that the lighter oil will flow easier than heavy weight oil. Correct speed, that is all down to personal preference IMO.
Get a syringe, fill it with water and squeeze it out, now do the same thing with engine oil
It takes more effort to empty the syringe filled with oil if you try to keep the same speed for the plunger
This is the principle when the fork oil is moveing thru the valve. The heavyer the fork oil, the more force (effort) it takes to move thru it.
haevy oil will make the front end feel stiffer (to a degree) and also feel harsh (crashy, rough or any other word you can think of) while thinner oil will make it feel less harsh and will in most cases allow the fork to follow the crappyness of the road better but more controlled as the tyre is still in contact with the ground, but there is a point where the strenght of the spring will be more than the oil/valve can control and you'll get too much bouncyness (anyone remember the movie "Uncle Buck" and the car he drove, that's the3 kind of boucyness I'm talking about - uncontrolled spring action)

Does that make sence of did I jsut ramble on

Good Rambling.

Sounds like logical rambling to me , specially the bit about the tyre staying in contact with the road

Update on the fork overhaul

Brought a set of .95kg/mm springs and seals from Shock Treatment. While I was there, ask what oil I should use and
they recommended 5w. They also suggested an extra 10 - 15mm preload spacer.

Since the install I've been on a couple of rides and have to say the bike feels a lot better. Way less dive when braking and rides over bumps a lot nicer.

Very happy.

Now waiting on my new BT023s and things will be even better.

Badger wrote:Update on the fork overhaul

Brought a set of .95kg/mm springs and seals from Shock Treatment. While I was there, ask what oil I should use and
they recommended 5w. They also suggested an extra 10 - 15mm preload spacer.

Since the install I've been on a couple of rides and have to say the bike feels a lot better. Way less dive when braking and rides over bumps a lot nicer.

Very happy.

Now waiting on my new BT023s and things will be even better.

How much did it cost you?

Hi Geekay007,

The springs cost $169 a pair and fork oil cost $20 a litre, used just over 1 litre so I had to buy 2 litres. Seals were $30 a pair.
Fitting was done at mates rates.

Sorry for the slow reply.

Cheers

Thanks Badger old boy

Instead of starting a new thread...

I'm not intending on replacing hte springs just get, just an oil change and wind up the preload a bit.
What the the weight of the *stock* oil? (my service manual hasnt arrived yet )