Teach me - fork oil
 

My Serow is over 20 years old. Slowly bimbling through checking everything.
Forks work and seem fine, but for a tenner its easy to replace the fork oil unless it lasts a lifetime?

What weight to choose - depandant on the rider weight, climate, stiffness required?
Type - Are all synthetic? Any brands to choose, Castrol, Rock oil, Silkolene etc?
Should it be a routine change, should it be combined with seals or not nescessary if they ok?

Re: Teach me - fork oil
 

<deep breath>
Fork oil eh.

Firstly yes replace it. Fork oil is one of those things that slowly goes off, you wont notice it but you will notice the difference between old and fresh.

Secondly weight, lol. Weight isn't really the best of things to describe fork oil, its rather inconsistent and basically has issues.

Essentially though what you put in all depends on the type of fork you have, older forks (ie the serow) are pretty much going to be damper forks (rather like the SV) and take ATF rather than fork oil, this in itself has issues because ATF does not have a specified 'weight' but rather a range, admittedly a tight one, this means that different makes (and even batches) may have different 'weights', as a result you should make sure you use the same batch (ideally bottle) to fill them.

You may find this article helpful

http://pvdwiki.com/index.php?title=Suspension_Fluid

Unless the seals are leaking leave them be, ideally you should totally strip, inspect and rebuild but tbh just fresh oil will make a world of difference. Even if it has drain ports on the bottom you're still better off taking the forks off, removing the springs and pumping them to remove all oil, put some fresh fluid in, pump the leg a few times and then drain again, this should remove all the old oil. Then fill with fresh, pump multiple times until no bubbles then measure from the oil to the top of the tube with the spring removed and the fork fully compressed, that is you oil height, add or remove oil until you are at the recommended height, extend the fork, pop the springs in and measure again, that gives you a figure you can work with later to add/remove oil if you want to tune things without having to take springs out etc.

Druid

Re: Teach me - fork oil
 

Thanks :)
I'm going to study what you have written and relate it to my bike.
I guess removing the spring is simply a case of undoing the cap and withdrawing it?
Pumping the fork, extracts the oil from the drain screw at the bottom or just tip it out?
Nothing will explode in a shower of springs and clips in the process?

Your link isnt bedtime reading lol.
The manual just states 10W fork oil - So I guess a 1L bottle of Silkolene will do the job?

Just found a youtube of it, well kind of. If only I read Japanese http://www.youtube.com/watch?v=tZJtrW39d1k

Re: Teach me - fork oil
 

i have been thinking about doing this to the sv but wasent sure how to go about it :/

instead of making a new thread could some one answer a few questions

1. what weight oil should i get, i weigh in about 17stone (ish)
2.can i just syringe the oil out as i cant be botherd to drop the forks
3. how much oil should i use for each fork leg?
4. is it as simple as it sounds ? EG jack bike up remove fork caps pull springs and other bits and syringe oil stick springs back in and fill with corect amount of oil replace caps

thanks PS sorry for thread hijack

Re: Teach me - fork oil
 

Well you can just syringe the oil out but you're not going to get rid of the crap in the bottom if you do that. Its better than nothing but no where near doing a proper job.

Druid

Re: Teach me - fork oil
 

On the serow I'm pretty sure yes, on bikes with adjuster screws in the top cap its a little trickier!

Turn it upside down, and then pump it.

No

It *is*, should send you to sleep in about 20sec.... ;)

This is where weight is 'bad' (see that link), different manufacturers use different 'weight' scales. However on a serow I doubt it matters much. ;)

Druid

Re: Teach me - fork oil
 

Why ATF for damper rod forks? Just use whatever viscosity of fluid suits what you intend to do with them.

Also a thorough cleaning job on damper rod forks doesn't matter so much, not like there's a valve stack to get bits of crud caught in is there?

I just dump in a pint of paraffin and swish it about to get the worst of crap out.



Barwel don't be lazy, do job right. You need forks off to set oil height correctly.

Re: Teach me - fork oil
 

So you can't get away with measuring the oil level with the bike on a front paddock stand suck the oil out with a pump and refill until at the same level as before?

Re: Teach me - fork oil
 

No if you change height at all then you affect how it behaves on brakes. I'm just going through this with mine 'cos it's not using a load of travel on the brakes.

But I know I started with 125mm air gap, you don't know where you started, so what's point of doing something to "improve performance" if you are going to throw in another variable.

Re: Teach me - fork oil
 

but if it's up on a paddock stand and held in situ then what can change.

Re: Teach me - fork oil
 

You don't know where you've started from. That's why I say measure it as per the manual then pop springs in and measure again, that gives you a base to work from.

Druid

Re: Teach me - fork oil
 

WRT to suspension tuning, stolen from http://www.peterverdonedesigns.com/suspension.htm

.5. Set approximate rear ride height.
1a. set Oil Height to the minimum height.
1b. Reduce rear shock nitrogen pressure to minimum spec.
2. modify the Oil Lock Piece - for race, eliminate or practically eliminate effectiveness of the oil lock piece. For street, reduce the effect of the oil lock piece if under hardest hit, more than 3mm of travel is left unused.
3. Spring Rate (& Sag) - this is done by changing springs (and preload).
4. Slow Speed Damping - this is done by changing oil viscosity and in some cases, slow speed orifice and needle size.
4.5 Straighten fork tube - these can be slightly bent. straighten the hell out of 'em.
5. High Speed Damping - this is changed by changing valves and/or shim stacks.
6a. Oil Height - this change tunes the last 1/5th of travel. Raise the oil height from the minimum if the fork is bottoming or practically bottoming.
6b. Rear shock nitrogen pressure should be raised in 25psi increments only to prevent cavitation.
7. Fine tune rear ride height for corner exit. Fine tune front fork clamp position for corner entry.
8. Re-sag bike.

Druid

Re: Teach me - fork oil
 

WRT oil 'weight' http://www.peterverdonedesigns.com/lowspeed.htm

I'll hot link the table in just to show:
http://www.peterverdonedesigns.com/i...osity-Data.gif

Also see http://www.peterverdonedesigns.com/damping.htm on the differences between damper rods and cartridge/shim stacks.

Druid

Re: Teach me - fork oil
 

I'm going to be stripping the forks on my CBR to get them powder coated soon. Can I re-use the seals even if I do that? I don't have a clue what the innards of the forks actually look like so that might be a stupid question. Will find out soon enough though, just want to check what bits I need, sounds like just oil if the rest is in good condition?

Re: Teach me - fork oil
 

These are RWU forks right?

If so you should be able to reuse seals, bushings etc. Just replace oil.

Re: Teach me - fork oil
 

Honda fork seals are cheap[1]. The grief of replacing them is immense. Odds are you'll ruin them taking the forks apart though.

Druid

[1] I don't know what model you have but CBR600F6 ones are £26, 'busa are £67!!

Re: Teach me - fork oil
 

Why ruin them? Slide hammer forks apart after removing clip, chances are they'll go back in OK.

Re: Teach me - fork oil
 

Silly question, but what's best to flush mayo & coffe grounds out of forks?

Re: Teach me - fork oil
 

Steamed milk :-P

Re: Teach me - fork oil
 

Latte? ;)

Re: Teach me - fork oil
 

Yup, I've got RWU forks - it's the one in my sig, a 2002 600F. I saw some seals (is it only a pair I need?!) on Ebay for about £6 lol! Is that risky or is it the case that seals are seals are seals?

I'd rather not spend £6 though, if it's pointless...I suppose since the forks are going off for powdercoating I'll have time to order the seals/other bits if needed.

Cheers for the help chaps.

Re: Teach me - fork oil
 

For the sake of £22 I'd not take the risk of them leaking when its a bitch to swap them again.

FWIW I wouldn't bother with the £6 ones, in my experience they don't last anywhere near the OEM ones.

Druid

Re: Teach me - fork oil
 

Hmm, ok - any tips on checking condition of them? I'll check them out before deciding, I think, I'm really trying to keep the cost down (hence the £6 comment!) as the spraying (bodywork, wheels, forks) is costing me £750 as it is. It's all contributing to a mind boggling £3500 sum of expenses this month, so the mrs tells me :?

Re: Teach me - fork oil
 

No, seals can look same when knackered or new. Dust seals can look all manky and rusty but be fine.

Re: Teach me - fork oil
 

Hardly likely old chap! It would be a little like re-using a wheel bearing after drifting it out with a hammer & punch.

I find that, on Jap bikes genuine fork seals last the longest, be they Honda, or Yamaha etc. It's the price of them that varies considerably.
Honda seals are reasonably priced, but you can only buy them with new dust seals. Mind you, the dust seals should ideally be replaced at the same time.


Cheers.

Re: Teach me - fork oil
 

What knocks them out is that washer above the top bushing, so they're getting driven out with evenly distributed knocks. Exactly same if not more precise than using a length of tubing to knock them in.

Re: Teach me - fork oil
 

Ok so £26 or whatever for genuine Honda ones would get me dust seals too, at least?

It's beginning to pale in comparison to the other costs this month...just been told about an upcoming bill for £650 as the mrs lost her passport this morning....

Re: Teach me - fork oil
 

Grandma suck eggs etc:D It's simply bad practise not to replace a component, that in terms of cost, is minimal compared to the aggro of doing the job as a whole.
We've all had to do it on occasion, & it usually turns out to bite one in the butt more often than not.


Cheers.

Re: Teach me - fork oil
 

£22+VAT+Delivery I believe for genuine Honda dust and oil seals from DSS.

Druid

Re: Teach me - fork oil
 

I agree, but you did compare it to knocking bearings out with a punch

Re: Teach me - fork oil
 

Well

I like saving money (YC corner)

and

I like knowing old bits have been replaced by new bits (Spannerman corner)

but

which do I prefer more?

there's only one way to find out.....




...fiiiigggghhhhttt!!

Re: Teach me - fork oil
 

I just reused my old ones, but that was because I'd revalved forks and chances are I'll want to do some other fine tuning which will require their removal at some point anyway.

Re: Teach me - fork oil
 

& of course the seals wont distort due to them being stuck in the fork slider Tightwad!!!:D:D:D

Re: Teach me - fork oil
 

There is nothing wrong with reusing seals, if they don't leak there is no need to replace them. You will not hurt them by taking them out.
If you want to take them of the tube make sure you clean tube first.

Re: Teach me - fork oil
 

nothing the beats the sight of fork oil spraying over the top yoke [1] the first time you hit the brakes with re-used / distorted fork seals, except maybe the sight of a bike scudding through traffic as the oil coats the brake disks and the rider is screaming like a girl [2]

[1] yes, it did actually get that high - some drops even hit me in the face
[2] well wouldn't you? with a face full of fork oil and no brakes???

Re: Teach me - fork oil
 

@phi-dan : Lmao Quite unique, I must say! Did you crash?

Re: Teach me - fork oil
 

If you take seal out, whack it with hammer and put back in than it is operator error, not seal.
No seal will do what you describing by simply taking it out and putting back in unless there are other issues.

Re: Teach me - fork oil
 

only issue was they were cheap pattern ones (with a lifetime guarantee - yeah right) and on inspection afterwards the inside of the seals were in a sorry state. They were also the ones without the solid washer in "to prevent distortion"...

btw I didn't "whack it with a hammer", I've changed many seals without having to resort to that and since then I have only bought OEM with no repetition of the above (much to my relief)

Re: Teach me - fork oil
 

Another Tightwad!!:D:D

Re: Teach me - fork oil
 

Just economically aware...