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Fork oil


trisaki

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trisaki

Hi guys  a question  for embee  how good is a fork oil with a Vi of 179  many thanks in advance mate 

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179 is fairly low, but not unusual for many oils I'd say. Fuchs/Silkolene RSF is around 330., the higher the better. When I've tried low VI oils I've found they tend to be a bit like treacle when cold especially if you use the bike in winter, feels like the forks have a broomstick left inside them. Castrol synthetic 10W was one I tried once, not nice at all (42cSt and VI of 150), too thick when warm and gets a lot thicker when cold.

There's a table here http://peterverdone.com/wiki/?title=Suspension_Fluid

 

Edited by embee
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trisaki

Thanx mate   will stay clear 

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Iron horse

How frequently should fork oil be replaced ideally? I'm doing mine soon when I replace the head bearings

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I'm not sure there is any hard and fast change interval, but I work on the principle that it starts to lose performance after around 10k miles typical use, so you might consider it a 16k service item.

Personally having changed it many times in different bikes I tend to do it fairly regularly, say every couple of years of my use, the cost is relatively small and once you get the hang of it is not a long nor difficult job.

A centre stand makes life much easier, weight (bag of sand) on the back of the bike and ropes to the garage roof from the handlebars to be sure. Wheel out, mudguard/caliper off, undo top yoke clamp bolt, slightly slacken the cap in situ, undo lower yoke clamp and the fork leg drops out (warning, hold on to it). Spring preload needs to be held down when undoing the cap but it's not excessive. Remove spacer, spring and washer. Turn upside down to drain, pump leg to get most oil out (usually filthy smelly stuff). Refill upright to a set level rather than quantity, fork compressed and spring/spacer etc out. Extend, refit the loose parts, fit cap (socket on ratchet and lean on it to compress spring, avoid cross threading!). Refit forks/wheel etc.

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Iron horse

Is it possible to take the forks out without removing the wheel? I.e. take the caliper off and slide both forks out at once?

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1 hour ago, Iron horse said:

Is it possible to take the forks out without removing the wheel? I.e. take the caliper off and slide both forks out at once?

Sure, or you could just turn the  bike upside down.

 

Sorry, now a serious answer. It's not difficult to remove the wheel and mudguard, and you only want to deal with one leg at a time. Can't imagine how tricky it would be trying to get the 2 fork legs plus wheel and mudguard out in one piece, big, heavy, and the bike would need to be a long way up.

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Has anyone tried sucking the oil out with a pump?

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fj_stuart
1 hour ago, djsb said:

Has anyone tried sucking the oil out with a pump?

 

Lidl did an oil suction pump a while back. Intended for engines but would work on forks (I think) For £12.99 it would seem to save a lot of hassle.

 

KsJeKuL5.jpg%20

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fj_stuart

My funny fork oil change story.

 

Many years ago I had a Kawasaki GPz 750 Turbo and decided to change the fork oil. A simple job - it had drain screws at the bottom of the fork legs. I got a basin in position and removed the drain screw. What I forgot was that the bike had air-assisted forks. Preload was obtained by pressurising the forks from a  valve.

 

When I removed the screw the oil was blasted out and spray-painted my garage wall!

  • Sigh 2
  • Haha 3
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Slowboy
8 hours ago, djsb said:

Has anyone tried sucking the oil out with a pump?

 

I don't think you'd get it all out, there's valves in the way. They really need to be out and inverted to drain properly.

 

its not so scary really😳

43050818660_df67e09403_b.jpg

 

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Sucking the oil out only removes about half of the oil in each leg.

Taking the front wheel out and unscrewing the bolt inside the bottom of the lower leg you drain 99% of the oil, with no other dismantling.

Quick and easy.

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3 hours ago, skorpion said:

Taking the front wheel out and unscrewing the bolt inside the bottom of the lower leg you drain 99% of the oil, with no other dismantling.

Quick and easy.

You've still got to undo the tops to refill, and if you want to set level rather than quantity of new oil you still need to remove springs/spacers, and with the wheel out you already have the caliper off and bike supported.

Sometimes the bolt in the bottom won't undo, it just turns the damper rod inside and you need to wedge it to hold it (tapered broomstick/dowel is the usual trick).

 

Just take the mudguard off and drop the fork legs, simple...………….. but it's up to you.

Edited by embee
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53 minutes ago, embee said:

You've still got to undo the tops to refill, and if you want to set level rather than quantity of new oil you still need to remove springs/spacers, and with the wheel out you already have the caliper off and bike supported.

Sometimes the bolt in the bottom won't undo, it just turns the damper rod inside and you need to wedge it to hold it (tapered broomstick/dowel is the usual trick).

 

Just take the mudguard off and drop the fork legs, simple...………….. but it's up to you.

 

You undo the bottom bolt before you take off the top nuts, that way the forks are still under tension and the bolts come undone easily.

 

Yes you are correct you have to also remove the springs and spacers to set the oil level, one thing I believe rightly or wrongly is the fork lowers get full of crud over time, and as you drain from the bottom these are more likely to flush out while draining,  when draining from the top this crud will go back through the fork valves/bushes and unless you also flush the forks some may stay inside.

 

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  • 3 months later...

Wondering what people have tried in their forks for oil? How have they found each. Thinking of doing my own instead of taking it to MCT suspension this time round obviously the feeling depends on rider weight and aggressiveness so just wondering if any have had a play around. Looking at the variations in cst between the oils it could be interesting playing around... not accounting for adjusting air gap!!

 

Not sure what make the chap at MCT put in but it's noted as 7.5w I think a little light maybe for me?

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This is an invaluable piece of info http://peterverdone.com/wiki/?title=Suspension_Fluid

Part way down there's a long list of branded fork oil with actual viscosities and viscosity index (VI).

I'm pretty sure the stock fork fill (at least prior to the dual bending valves, don't know for those) will be either Honda Pro HP 10W or Showa SS-8 (10W), either way it's about 35cSt viscosity at 40C. A high VI is desirable as this indicates how much the viscosity varies with temperature, higher VI= less variation.

 

I use Fuchs/Silkolene Pro RSF 7.5W (it is now marketed as Silkolene "Maintain" RSF). You will see that it is actually very much like a typical 10W oil (37cSt at 40C), but has a significantly higher than average VI (322)

 

Once I tried some Castrol synthetic 10W, which according to the list has a viscosity around 40cSt but the VI is only 150 compared to the Silkolene RSF at 322. I found the Castrol, to be OK when warmed up a bit, but when cold the forks felt like they were filled with wood.

 

I'd suggest pick something around 35-40cSt with as high a VI as you can find, the Silkolene Maintain range works very well in  y experience. Don't just go on the label grade, there can be a huge difference between different brands.

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embee yes thanks had a look a charts and just been on various sites looking at cst..VI.

 

Did you leave air gap as standard?

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2 hours ago, giley said:

Did you leave air gap as standard?

I have the Integra so similar suspension details to the S model. I have emulators fitted so damping is quite different to the stock set up, however when I visited K-tech to get some springs for it I discussed the issue with them and they were quite adamant that I should try setting the oil level quite a bit lower than Honda's recommended value. In the Integra the book says 103mm I think, I am currently using 140mm if I remember correctly, and use the Silkolene Maintain 7.5W.

Others have done quite a bit of playing around with the X model, so may be along shortly to give advice. The oil level is one of the easiest (and cheapest) things to alter so I'd recommend experimenting a bit, you can always just revert to standard.

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Thanks, might have a good play around when weather warms up a bit. Not really sure what I am after so would be interested in "feeling" the differences. While I'm awaiting funds for new/2nd bike :-)

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5 hours ago, giley said:

 

 

Did you leave air gap as standard?

 

On my 2017 750x I found Silkolene "Maintain" RSF 5w with a 150mm air gap works far better than standard.

On the 750x, Do Not use the Honda standard air gap of 180mm with 5w oil as the forks have too much dive when braking.

 

I checked the forks sag and mine was 75mm so half of the overall fork movement taken up before riding, so I bought the Chinese 41mm preload adjusters from that auction site & now have set it at 45-50mm sag so I have 100mm of fork travel left.

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wingrider.steve
On 10/14/2018 at 23:28, fj_stuart said:

My funny fork oil change story.

 

Many years ago I had a Kawasaki GPz 750 Turbo and decided to change the fork oil. A simple job - it had drain screws at the bottom of the fork legs. I got a basin in position and removed the drain screw. What I forgot was that the bike had air-assisted forks. Preload was obtained by pressurising the forks from a  valve.

 

When I removed the screw the oil was blasted out and spray-painted my garage wall!

I once had exactly the same problem on a GL1100 Goldwing only it was me that got sprayed with oil!

Ah well, it's the sort of thing you only do once!!

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Rocker66
5 minutes ago, wingrider.steve said:

I once had exactly the same problem on a GL1100 Goldwing only it was me that got sprayed with oil!

Ah well, it's the sort of thing you only do once!!

Talking of the GL1100 I wish that modern bikes had the air adjustable rear shocks that my Aspencade version did.

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I change the fork oil when I change the front tyre now, which is usually just over every 10k, if I'm taking the mudguard \ wheel off anyway might as well do it then.

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