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Author Topic: Fork oil capacity?  (Read 6036 times)
toniplavna
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« on: February 07, 2012, 03:35:54 PM »

I have gpz500s 1996 and I read that fork oil capacity is: dry 352ml, oil change 300ml. Some others say dry 287, oil change 245ml. So what is true?  Huh
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naturalphenomenon
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« Reply #1 on: February 07, 2012, 06:17:16 PM »

i always put extra in, i have talked to quite a few suspension experts it doesn't hurt as long as it doesn't blow the seals
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toniplavna
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« Reply #2 on: February 07, 2012, 06:28:19 PM »

Ok but 352 and 287ml is a big difference. Probably 352ml is for 94 and up models and 287ml for 87-93 but I am not sure Undecided
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montnrdr
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« Reply #3 on: February 07, 2012, 07:04:08 PM »

Ok but 352 and 287ml is a big difference. Probably 352ml is for 94 and up models and 287ml for 87-93 but I am not sure Undecided
You are correct, 352 is 2nd gen and 287 is 1st gen.
Also fork oil level is important as it will affect your compression and  rebound.
read this for more info:
http://www.ex-500.com/wiki/index.php/Fork_Maintenance
This is a great and inexpensive tool that make the job much easier:
http://www.amazon.com/gp/product/B000GZPCYI/ref=oh_o00_s00_i00_details

or this will work also:
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toniplavna
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« Reply #4 on: February 07, 2012, 07:25:43 PM »

Ok thank you  Wink
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bmetz99
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« Reply #5 on: February 08, 2012, 03:06:40 PM »

i always put extra in, i have talked to quite a few suspension experts it doesn't hurt as long as it doesn't blow the seals

Not sure what experts you're talking to, but this is potentially bad info.  Going an extra 5cc or so won't make a huge difference, but understand that the air gap above the fork oil also acts as a spring.  The higher the oil level, the smaller the air volume, but the greater it gets compressed for a given amount of fork travel.  You can actually compensate for too-weak fork springs by raising the oil level, to a limited degree.  There is enough effect on spring rate that you can't just make a cavalier statement that oil level doesn't matter so long as it doesn't blow seals.
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piterus
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« Reply #6 on: February 08, 2012, 04:21:39 PM »

7.5cc will raise 1cm oil level (37mm forks)
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dad
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« Reply #7 on: February 08, 2012, 09:58:31 PM »

Here is a link to a specific post on fork oil buried in a very thorough suspension thread, the why's as well as the method. An additional search for "fork oil level" as posted by "dad" will get even more replies to posters doing this work with some further good tidbits flushed out. It's good knowledge to have. Good luck. Cool

http://www.ex-500.com/index.php/topic,702.msg8244.html#msg8244
« Last Edit: February 08, 2012, 10:00:14 PM by dad » Logged
toniplavna
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« Reply #8 on: February 09, 2012, 06:36:44 AM »

Ok guy I will put 300ml and thats it. Thank you all
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moped
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« Reply #9 on: February 09, 2012, 09:06:45 AM »

Forget the fork oil capacity and use a $1 turkey baster to measure the fork oil level. It will be more precise and easier to measure.

http://www.ex-500.com/wiki/index.php/Fork_Maintenance

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FOG
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« Reply #10 on: February 09, 2012, 09:36:45 AM »

i always put extra in, i have talked to quite a few suspension experts it doesn't hurt as long as it doesn't blow the seals


Blind logic like this is the bane of all Mechanics.

The air gap at the top of the fork above the oil level is a component of the spring rate. It has a compression ratio. It is a bit of fine tuning, if you have a functioning brain that can figure out how to use it.   Doing stupid shit like the above comment is the surest way to defeat and design feature. They even put a note on the oil filler to not overfill.
Gee why wouldn't a little extra be better.
Dumbkoff. would better describe your "experts"

FOG
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moped
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« Reply #11 on: February 09, 2012, 10:03:16 AM »

i always put extra in, i have talked to quite a few suspension experts it doesn't hurt as long as it doesn't blow the seals


Blind logic like this is the bane of all Mechanics.

The air gap at the top of the fork above the oil level is a component of the spring rate. It has a compression ratio. It is a bit of fine tuning, if you have a functioning brain that can figure out how to use it.   Doing stupid shit like the above comment is the surest way to defeat and design feature. They even put a note on the oil filler to not overfill.
Gee why wouldn't a little extra be better.
Dumbkoff. would better describe your "experts"

FOG
I would question if your suspension experts even know how hydraulic forks work if they have given you that opinion. As Fog has said setting the air gap precisely at the top of the fork is critical. The trapped air serves as an extra spring when you get close to bottoming out. Too much oil, even a little bit, reduces the air gap and will cause hydraulic lock which is much WORSE than too little oil and a larger than ideal air gap.
« Last Edit: February 09, 2012, 10:06:29 AM by moped » Logged
dad
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« Reply #12 on: February 09, 2012, 11:09:03 AM »

That's why it would be a good idea to read the whole thread that I linked above. It explains the reasons for all of this stuff, how and why it works, then expands on that understanding with some changes that can be made to meet your own conditions (most important variable, the weight of the rider).

Even when no mods are to be made, the understanding and methods don't change and the understanding lets you make good, correct decisions. Like how critical the oil level is. 1/2" to maybe an inch level overfill, not a HUGE deal that will make things grossly unsafe, cause wheels to fall off or lock the front suspension to where there's no travel having it bound (hydro-locked) at half of what it should be. But if you're heavier and aren't putting in the right springs for your weight, maybe overfilling by as much as an inch wouldn't be a bad idea. Meanwhile 5" overfill is definitely bad news. Read the link and learn why this is.

But, if you ARE putting in the right springs, stiffer this time to the proper rate for a heavier rider's weight, why you should put in less oil than originally speced, and then how to verify after some test rides if the choice was ok and if not, which way to go with it. You've got a chance of understanding this and even how to watch the functions after completed to determine if what you did is ok. Point is, take time to read and understand. Knowledge is power. Wink Good luck. Cool
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FloridaEX500
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« Reply #13 on: February 09, 2012, 12:01:18 PM »

He's just another "Goombah", that's what I was called when I didn't know a darn thing about construction. My first boss- the GC called me that. I think it applies here. LOL
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dad
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« Reply #14 on: February 09, 2012, 12:12:48 PM »

He's just another "Goombah", that's what I was called when I didn't know a darn thing about construction. My first boss- the GC called me that. I think it applies here. LOL

We were all that guy at some time in our past. Wink That changes in direct correlation to our willingness to learn. I try not to criticize the absence of knowledge but encourage acquiring it. In fact, I just did. Smiley As we eventually learn, the hard or the easy way, none of it is magic, just knowledge.

I also say, "You can lead a horse to water, but you can't stop him from pissing in it". I don't know if that fits but I like saying it, so I did. Wink Grin

Really, good luck. Smiley
« Last Edit: February 09, 2012, 12:14:23 PM by dad » Logged
bmetz99
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« Reply #15 on: February 09, 2012, 03:44:23 PM »


We were all that guy at some time in our past. Wink

No, not all of us.  Matter of fact, most of us know to keep our mouth shut when we don't know what we're talking about.  One of the worst things about a forum like this is the small minority of people who feel compelled to give ill-informed "advice" in the guise of "helping".  Someone seeking assistance ends up misled by someone who needs so badly to feel like an authority that they'll post utter bullcrap.  And the person who thought they were getting actual, useful, well-reasoned information ends up making things worse.  So you end up with a page full of responses meant to correct the misinformation that shouldn't have been posted in the first place.

There's nothing wrong with not knowing something; we all started out not knowing a box end wrench from a feeler gauge.  That's what makes this forum, and others like it, so valuable- there's a wealth of great information available from people who have spent years learning this stuff, and who are happy to share.  But for crying out loud, if you don't know what you're talking about, either look it up or wait for someone who does know what they're doing to come along.

Otherwise you end up with an unfortunate situation.  As a wise man put it:

Quote
"You can lead a horse to water, but you can't stop him from pissing in it".
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piterus
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« Reply #16 on: February 09, 2012, 05:06:01 PM »

i always put extra in, i have talked to quite a few suspension experts it doesn't hurt as long as it doesn't blow the seals
so, there is a relationship betwin high oil level and seal durability then?
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jchiasson
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« Reply #17 on: February 09, 2012, 05:14:09 PM »

Durability ... I don't think so. But at some point between the high oil level and the compressed air it will compromise the actual sealing ability of the seal.
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« Reply #18 on: February 09, 2012, 05:31:20 PM »

i always put extra in, i have talked to quite a few suspension experts it doesn't hurt as long as it doesn't blow the seals
so, there is a relationship betwin high oil level and seal durability then?

Overfill the forks enough and you'll blow the seals.

Let's walk through an example.  You fill the fork with the tubes collapsed.  Say, for the sake of argument, you start with 5 inches of air above the oil, and the fully-extended forks give 5 inches of travel, so you've got 10 inches of air above the oil.  If you use up all of the fork travel, you compress that air space down to 5 inches total.  You half the volume, so you double the pressure.  If you start with atmospheric pressure (about 15 psi) in the forks, you have 30 psi in them at full compression.

Now let's overfill the forks by 2 1/2 inches (only 2 1/2 inches of air when you fill them, and 7 1/2 inches of air when fully extended).  Now at full compression you've reduced the air volume to one third of original (gone from 7 1/2 inches of air to 2 1/2 inches of air).  And you've tripled the pressure in the forks (45 psi).   The fork seals are designed to keep fluid in place over a sliding mating surface, not withhold extremes of pressure.  At some point you'll overcome the seals' ability to hold pressure, and end up physically deforming them (and now your seals are shot).

An oversimplification, but in essence what happens.
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dad
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« Reply #19 on: February 10, 2012, 10:24:29 AM »

For what it's worth, on sportbikes, best fork oil level with the proper springs will typically fall in around 5" to 5 1/4" down in the tube, springs out, fully compressed. That's because the variables on forks aren't so great in sportbike weights and the service conditions. These have very soft springs in them so use a higher than typical fork oil level to add spring progressivity, trying to compensate for the heavier riders that will wind up on them without being too dangerous, with limited success. Undecided

The factory spec on these is 4 5/8" down, pretty high on average, higher than it would be with the optimum springs, but due to the factory not knowing the weight of the rider purchasing one and their very soft stock springs. The suspension on these is full of compromises due to not knowing the rider variables and.... I still don't really know why they spring them so absurdly softly, but.... I'd hate to think it's to make their other bikes feel so much better and justify an "upgrade" to another bike ar a later date but I really can't think of any other real reason. And if it's true, that's not very nice. Sad Not nice at all. Wink But it can be fixed as outlined in other threads. Cool

And one more anecdote from my own experience. I have older CBR-1000F's as my street bikes, touring bikes. They are heavy (608#) Shocked and as such, never even had the ready option of changing springs because nobody even offered one stiff enough. And the stock ones weren't THAT bad for all but hard riding. They also came with Honda's first cartridge shocks, nice for the time. What was particularly annoying with the stock front was the propensity for bottoming out under hard braking and hard riding, especially at the track. Yes, I track rode it sometimes. Smiley When deliberating what to do with it, excessive static sag and propensity to bottom under hard braking, and then seeing that the stock fork oil level spec was something like 6 7/8" down in the tube, I decide to go with a new spring spacer to get the static sag up from 2 1/2" to 1 3/8" and raise that fork oil level to add progressivity and then settle for whatever improvement I got. Ran it as high as 4 3/8", a full 2 1/2" higher than spec, and did fine with it. It would still bottom under the most extreme braking but was still way better all around, helped the bottoming except in the most extreme braking. And the point in adding this story, the oil level was first changed on that bike when it had about 25,000 miles on it and the fork seals never leaked until after 90,000 miles, at least half of which was put on working it pretty good on extreme mountain twisty roads. And when they did finally fail, it was the typical environmental damage and age that did them in, not just the wear from repeated sealing of pressure. I don't know that I would go more than that on any bike and for the reason that the real design and service parameters are really similar, one bike to another (that's why I did what I did but didn't try more), but they aren't glass, either. I hope that adds something specific to the conversation but doesn't it really encourage reading up all the more? Gain some undertanding of these parts even if no change to hardware will be made?  Cool Good luck, all!
« Last Edit: February 10, 2012, 10:45:39 AM by dad » Logged
FOG
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« Reply #20 on: February 10, 2012, 10:35:03 AM »

Just some more enlistment. The "too much oil will blow you seals" Is another old wife's tales right up there with "Loud pipes save lives"  Or total BS.
Even completely full fork  (Hyd locked) would not "Blow" the seals. Much more like likely to bend the frame first. the seals are designed to be pressed against the sealing surface by the contained pressure. and will continue to hold their "seal" way past the time where the HYD locked forks will bend the frame beyond rid-ability.

The area of the seal exposed to the pressure is very small and can withstand pressure in excess of 100,000 PSI.

Next time your "Expert spouts such foolishness find another expert.

FOG
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bmetz99
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« Reply #21 on: February 10, 2012, 11:22:58 AM »

Just some more enlistment. The "too much oil will blow you seals" Is another old wife's tales right up there with "Loud pipes save lives"  Or total BS.
Even completely full fork  (Hyd locked) would not "Blow" the seals. Much more like likely to bend the frame first. the seals are designed to be pressed against the sealing surface by the contained pressure. and will continue to hold their "seal" way past the time where the HYD locked forks will bend the frame beyond rid-ability.

The area of the seal exposed to the pressure is very small and can withstand pressure in excess of 100,000 PSI.

FOG, while I respect your experience and expertise, this raises a few questions.
Dirt bikers and off-roaders routinely blow fork seals from hard landings.  Intuitively, the sudden spike in pressure from a hard landing would do this.  But if, as you state, a fork seal is good for 100,000 psi, why would this happen?

I worked for a number of years with diesel-powered liquid abrasive cutters.  These generated 40,000 psi,  I had frequent occasion to rebuild these pumps- they used ceramic pistons the size of a pencil, and  the seals were made of a hard plastic with VERY little give- nowhere near the flexibility of the rubber seals used in forks. Inserting the pistons was a bit of a chore- the sliding friction was substantial, even with an ultra-smooth ceramic piston.  There's no way this sort of seal would be sueful in something like a motorcycle fork-the seal stiction would prevent the freedom of movement needed for a supple, useful suspension.  So if such an ungiving seal is needed for a mere 40,000 psi, how is it that a fork seal is good for 100,000 psi?

Thanks, as alsways, for your insights and shared experience.
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« Reply #22 on: February 10, 2012, 01:50:21 PM »

Those dirt bike seals where probably worn or damaged from being,well  dirty.
Your experience with Hyd equipment supports what I was saying. The 100,000 PSI might have been a exaggeration ,but my point is that your forks won't generate enough internal pressure to actually blow out a seal in otherwise good condition

FOG
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bmetz99
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« Reply #23 on: February 10, 2012, 03:48:06 PM »

Those dirt bike seals where probably worn or damaged from being,well  dirty.
Your experience with Hyd equipment supports what I was saying. The 100,000 PSI might have been a exaggeration ,but my point is that your forks won't generate enough internal pressure to actually blow out a seal in otherwise good condition

FOG

Hmmm...  Don't most dirt bikes run fork gaiters any more?  And what about the street bike riders who blow seals from landing hard wheelies?  Do fork seals only go because of pitted/dirty fork tubes?


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« Reply #24 on: February 10, 2012, 04:50:10 PM »

It's entirely possible that the pressure inside a dirt bike fork exceeds My hypothetical 100 k value. We need some numbers on the forces involved.

FOG
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