Fork Oil - Level or Quantity

[Squeeze]

I'm changing Fork Oil on my '93 and stumbled across something weird.

 

In the Manual i downloaded from here, Yammi states to fill 409 ml of Oil in each Fork Leg. As i'm no Friend of this Way, i measured the Air Chamber after the proper Fill.

 

This Amount of Fluid leads to a Air Chamber (or eventually Oil Level) of 245 mm without Springs and the Legs compressed. Imho, that's way too much Airchamber for a Travel of 140mm.

 

I researched the same Shop Manual and in the Specs Summary Yammi states a Oil Level of 172 mm. As the Reference of 'Oil Level' isn't stated, i assume they take the Measurement between Top of Oil and Top of the inner Fork Tube which is the Air Chamber.

 

I researched a Lot of Fork Oil Threads here and got inconsistent Results. A Member stated to buy 2 Quarts others didn't mention any Kind of Quantity.

 

Basically and my first Question to those who have done that in past would be:

 

How much Oil do i need to refill both Legs ?

 

 

It could be either 409 ml per Leg and have a real big Air Chamber or something around 540 ml per Leg which would lead to an Air Chamber at 170 mm.

 

All other Forks worked on in my Life have had around 10 Percent more Airchamber than the Fork Travel was. This Formula would lead to an Airchamber with 155 mm.

 

Maybe this is the Answer to some bad Behaviour of the front End which some 1Gen Rider suffer from.

[Squidley]

Lutz,

I'm not sure of the ML to Fld oz but I have always put 13.8 fluid ounces (yes as it says in the book) and haven't really had any issues with it like that. If I'm not mistaken when progessives are installed they recommend 5 inches from the top of the tube with the tubes compressed. I'll be interested in hearing from others on their experiences with it.

[Rick Butler]

Lutz,

 

Any more I have stopped dealing with fork fill capacities, especially if you don't remove the forks and let them drain upside down. I now use the method of measuring the distance from the top of the tube to the oil level, with the forks completely compressed. And for most forks like ours with a total travel 5.5", 5" works pretty well. What this is doing is leaving enough expansion area for the forks to fully compress (which you will never do). And another reason for using this method is that you always get the same amount of oil in both forks, where if you still have a little oil left in one leg (over the other) and add 12 oz to each fork then you will end up with different levels.

 

Hope this helps,

 

Rick

[Squeeze]

Rick, i'm very familiar and aware with the Fork Situation.

 

I agree on everything you said. This darn Fluid Amount Statement is just plain the wrong Way. This should have been forbidden since 50 Years. What bugs me, besides the Fact that Yammi states way different Facts about the same Issue in the same Book. Not that they aren't know for such Things, but as we're talking Suspension here, not a messed up Carb Synch. Imho, it's better to acknowledge the Facts, set them Straight and secure that the Message is spread out.

 

I've seen a Lot more than 20 Forks, and i always use a clear Can to drain and pump the old Fluid out, check the Fluid for Colour and Quantity. When you ask the Owner why there is so much more Fluid in one Leg than in the other, it's always the same Answer 'Hey, i just filled it up as the Book said'. Usually my next Question is 'and you didn't notice any negative Change of the Ride afterwards ?' and the Answer is 'Yes, but i thought i have to blame the new Tire or my bad Adjustment on the Steering Head'. Now, with the Air-linked Fork Tubes, as the 1Gen's have, this is not extra dramatic, but without any Connection, you will be in deep Trouble. There is nothing which can held up against the Forces of different compressing Forklegs, no Superbrace, no Wheel Spindle, nothing.

 

I'm sorry that there are not more Comments, but i think we should keep this Thread alive, because this is important for all our Bikes and the correct Fluid Level and Procedure is also important for the 1Genners.

[Tupperj]

Squeeze,

 

I agree that this is really good information to get out. Can we come to a consensus as to the appropriate fluid level for the various models? And does having Progressive springs change that value at all?

 

I'm in the process of "cleaning up" the PDF service manual that's available, putting in some missing pages and such. I'd be happy to add an addendum if we can come up with an appropriate table.

 

What do the guru's think?

 

Paul

[Condor]

Squeeze. I thought I might toss in a couple of comments, good or bad, just because. When putting 409ml in the fork tube and not getting anywhere near the 5.5" perhaps it's because it's not really needed. I don't know about the other bikes, but with the class system or 2ndGen manual pressure system, pressures applied to the air chamber may limit compression, and rebound and dampening might be more of an issue. And the larger air chamber might be done to give a greater amount of adjustment to fork air pressures. Just my warped thinking kicking in??????

[Squeeze]

I'm i the Process of making up my Mind about the Air Chamber Height.

 

The Fork travels 140 mm/5.5 Inches. As i don't want to have any Fluid pushed inside the the Air Lines, the Level needs to be beneath the Hole for the Air Connector on the inner Forkleg plus some Reserve to ensure this when the Fork is full compressed and with the Springs mounted.

 

This will probably come out at the 172 mm of Oil Level without Springs which Yammi stated in the Book.

 

I will go after this later today and report back about my Findings.

 

Regarding the different Displacement of Progressive Springs, i can't say anything. I've never seen a Set of those and compared them to stock Springs.

 

From what i've seen on other Bikes, Aftermarket Springs compared to the stock Springs are not so much different in Displacement. Heavier Aftermarket Springs might have 2 Percent more Displacement, would be my Guess. Not that those 2 Percent would make a big Deal, but it's not only academic.

 

Maybe it's Time to make a good Writeup for the Fluid Settings.

[EddyG]

I am a new Venture owner, just bout it last Sunday. As with any vehicle I buy I go thru it before I start to drive it, a bike to me is even more important.

 

I have skimmed the manual, but If I am reading these post right, I would drain the fluid, checking the quanity out of each strut. But when i fill it. Measure down from the top, 5 to 5.5 inches, making sure both struts are even. Then the air charge. And this should get them right. What oil should be used and how much??

 

I noticed the wheel wobble as I drove the bike home, and I hope this is part of the problem. I had also found the rear tire VERY low on air.

 

Thanks

[Props]

I just finished installing Progressive fork springs in my 89VR about 3 weeks and 1500 miles ago... man, what at huge improvement over stock! They are MUCH different in size and thickness... much more than the 2% mentioned above... wishing now that I would have taken pictures to show just how much difference there really is. Using the Progressive instructions to measure the 5.5" from top of tube to the top of the oil is the ONLY way to get the fluid levels right. Just using fluid measures will almost guarantee that you will have unbalanced oil levels and have handling issues.

[Squeeze]

Squeeze. I thought I might toss in a couple of comments, good or bad, just because. When putting 409ml in the fork tube and not getting anywhere near the 5.5" perhaps it's because it's not really needed. I don't know about the other bikes, but with the class system or 2ndGen manual pressure system, pressures applied to the air chamber may limit compression, and rebound and dampening might be more of an issue. And the larger air chamber might be done to give a greater amount of adjustment to fork air pressures. Just my warped thinking kicking in??????

 

Jack, i'm with you on a larger Air Chamber allowing better Adjustment, due to the larger Amount of Air needed to built up any Pressure at all. But nearly all the Bikes i worked on have had an Air Valve to fine tune the Settings. The early Maxxes have the same Connecting System as the Ventures, the later Maxxes have single Shrader Valves on the Top of each Leg, my Hondas have had them in both Ways. But all these other Bikes have one Thing in Common, a way smaller Air Chamber than Yammi states as a Result of the filling each Leg with 409 ml of Oil. That's where my common Sense kicks in and says 'Stop !' and think about it.

 

Basic hydraulic Damping and Rebound isn't affected by the Pressure of the Air Chamber in the Legs. The overall Damping is affected from more or less Volume of Air in the Air Chamber and the corresponding Pressure that builds up by the Compressor during filling or the Fork compressing during the Ride. You change the Behaviour of a basic Suspension by setting them on different Oil Levels and even limit the Travel when you overfill the Legs.

 

But if you want to have a good Suspension you need to do first Things first. Basic Setup is to ensure that both Forklegs have the same Fluid Level. As Rick stated, and i fully second his Statement, the Quantity Method isn't anywhere near as accurate as it should be.

 

Once you got the same Level in both Legs, you can play with different Levels and test ride them all. I really thought about mounting Shrader Valves to the top Heads of the Legs for easier adjustment. I will figure out a Level later, and if i don't like the Outcome, it will go that Route.

[rhncue]

Lutz,

 

Any more I have stopped dealing with fork fill capacities, especially if you don't remove the forks and let them drain upside down. I now use the method of measuring the distance from the top of the tube to the oil level, with the forks completely compressed. And for most forks like ours with a total travel 5.5", 5" works pretty well. What this is doing is leaving enough expansion area for the forks to fully compress (which you will never do). And another reason for using this method is that you always get the same amount of oil in both forks, where if you still have a little oil left in one leg (over the other) and add 12 oz to each fork then you will end up with different levels.

 

Hope this helps,

 

Rick

 

Boy, did I screw up. I put progressive springs in my 83 around 7 or 8 years ago. The bike has been bottoming out and sitting lower than it should so I got some new Progressives last week for both front and back. I screwed up there as the old ones were the exact same length as the new ones. Oh well. I drained the legs and one side was low on oil and the other side barely had any oil at all in it. I thought I followed the directions for installing the Progressives and filled the legs to 5.5 inch from the top, put in new springs and put the rest back together and took a ride. It rides very smoothly unless I run over a sewer lid or such and then it's as if it bottoms out. Still a pretty rough ride.

 

Upon reading these replies I see that I made a major BooBoo. I never compressed the forks. I put fluid in 5.5 inch from the top with the legs extended! No wonder it is such a rough ride. No where for the oil to go. I was wondering why it took more than a quart to fill both sides when the directions called for less than 14oz. per leg. I'll have to go drain and refill the forks later this afternoon. I think I've become completely senile when I don't comprehend the difference between compressed and extended.

 

Dick :rotf:

[GeorgeS]

In all the bikes I have owned over the years, I simply Drained, and Refilled each side,

with the " Measured " amount called out in the Service Manual.

 

Never had a problem with this method.

 

When Installing the New Progressive Springs in my 89, I put in 1 Oz Less then the Yamaha called out required amount. Obviously due to the Increased Diameter of the Spring Material.

 

I decided to try 15Wgt Fork Oil, and No Air pressure.

 

Ride was a little stiff at first , however seems to be just right after 8K miles on the new springs.

 

Or, I just measure out accruatly the Number of OZ of Oil in a seperate container, and dump in that much. I have never bothered to Measure the air space with forks compressed.

 

Both sides should come out the same with this method.

[Gearhead]

I've not worked on nearly as many bikes as Squeeze, but FWIW...

 

I've usually done what GeorgeS does - use the volume method. I am always careful to get a complete drain by allowing them to drip for a while, then pump the sliders up and down a few times. If I'm not taking the forks apart, I put some ATF in them, stroke them, and drain them again to flush the old gunk out. Last time I did the Venture, when I put in the Progressives, I did this, filled with factory volume, then for the first time I made a detailed measurement of level. They weren't identical, but were very close, probably within a half inch. If memory serves, the level was around 6 or 6.5".

 

Comment on level - air trapped in the bottom will throw the level way off. After adding new fluid, burp the forks by sliding the sliders full travel a few times.

 

Comment on Progressive's recommendation - the instruction sheet we all got is the same one they send out with all their fork springs. 5.5" is not a finely-tuned setting for the Venture, but rather a generic safe level to ensure there is still a little airspace with the spring and cap installed. And I would say the Progressives occupy quite a bit more space - they are longer, with thicker wire and more windings.

 

The airspace accomplishes two things: allows room for the volume of the spring, and allows some minimum space for the air to compress into. The smaller the airspace, the more the air that's in there has to compress and the more progressive the fork becomes due to the spring action of the compressed air. I dunno if "more progressive" is good or bad. However, any air pressure, whether due to compression forces or due to air put in by the rider, exerts pressure on the fork seals and I think causes them to wear out faster.

 

I've never heard this rule of thumb before, about wanting the air chamber to be the travel plus 10%. If you assume the spring takes up the 10%, then what that means is from fully extended to fully compressed you compress the air to half its original volume. Cutting the volume in half doubles the absolute pressure. Hmm...probably the compression % is a little higher because the cap also takes up about an inch.

 

I would think that once you reach some critical amount of oil to fill the bottom of the fork and lube the piston, the primary effect of changing oil level is effective spring rate. I don't think the damping mechanism is going to care if you raise or lowering the level an inch or two, as long as the orifices and piston chamber stay filled, right?

 

EddyG, I can't totally get rid of the wheel wobble on mine.

 

Dick, that is funny, but it could happen to anyone. Glad you didn't damage anything.

 

Jeremy

[Squeeze]

Well, i figured it out.

 

The Oil level has setted over night to 250 mm Airchamber without the Springs. The Distance from Top of the Fork Leg to the Air Connector Hole is 60 mm.

 

The stock Springs are with 23 Windings inside the Oil after mounting. This equals to 2.33 mm per Winding, or an Air Chamber with Leg compressed and Spring setted into the Leg at 195 mm.

 

Now, we do some Math and find 135 mm of Travel plus 60 mm have to remain under Air any Time, which makes the Air Chamber with Spring at 195 mm. Yammis stated in the Specs 197mm. It seems my 195 mm are the Answer to the Question 'What is the Oil Level of a MKII Fork defined by Yammi Specs?'

 

The Facts are:

Stock Spring

full compressed Fork Tubes

no Spring attached

Airchamber more than 250 mm from Top of the inner Tube

[Squeeze]

George, as Rick wrote, the Amount Method doesn't work out right in most Cases. The only accurate Method is to measure the Levels and basically ensures both Legs travelling the same Way and keep them parallel during mechanic Movement.

You have to remember, most of the Springs are progressive nowadays. Which basically means that you amplify the Effect of different mechanical Damping on every Point of the Travel by different Air Pressures which are inherent at different Oil Levels.

 

 

Jeremy, your right about the Math and about the Springs taking up the 10 Percent Air Chamber. But if you keep the Oil Level high, it doesn't effect the mechanical Damping and Rebound, but makes up an hydraulic Stop before the Fork bottoms out mechanically. This is a much smoother Stop than letting the Tube bang on the Ends. If you want to limit the overall Travel of the Legs, you can overfill the Legs. But this doesn't apply to our Forks, because pressing Oil in the Air Lines is not a good Idea, to say it at least.

 

Now, all that said, to point it out once more, some of our Bikes seem to have an incurable Tendency to express a Wobble under certain Circumstances, we can't do much more as to ensure that all the Basics are right to to the Point. My Venture does it also, and i hope i can report good or at least better News when i got it back on the Road.

[rhncue]

A week or so ago I put in new Progressive springs even though upon measuring I found that my old ones weren't bad. However when I put in the oil I put in to much as I put in 5.5 inch from the top of the tube but with the forks extended instead of collapsed. I just went out and pulled the springs and drained some oil to correct my mistake but when I tried to collapse the tubes they won't move. I have the bike in the air on a jack with the springs out but when I lower it to the ground they don't collapse at all.

 

I weigh close to 300 lbs and I know this bike rides very roughly. I rebuilt the front forks with new seals and bushings about two years ago but something is amiss. When I get on the bike, as heavy as I am, it doesn't feel that the forks collapse at all.

 

What's up?

 

Dick

[Squeeze]

Dick, that doesn't sound good. The Tubes should run with very very low Resistance to compressed and expanded End. When i have the Legs in the Bike without a Spring or Wheel mounted, the Legs slide slowly to full expanded just by Gravity.

 

I guess, there must be something stuck inside ? Is the front Wheel still mounted ? If so, what happens when you open the Pinch Bolt and loosen the Front Axle ?

[rhncue]

Dick, that doesn't sound good. The Tubes should run with very very low Resistance to compressed and expanded End. When i have the Legs in the Bike without a Spring or Wheel mounted, the Legs slide slowly to full expanded just by Gravity.

 

I guess, there must be something stuck inside ? Is the front Wheel still mounted ? If so, what happens when you open the Pinch Bolt and loosen the Front Axle ?

 

The legs look fully extended, they won't collapse. I don't have the wheel off. I did lossen the Super Brace as the directions that came with the Progressive springs says this is a major cause of forks not operating correctly. I will go out right now and loosen the pinch bolt and see if this has any affect.

 

Thanks, Dick

[rhncue]

I just loosened the pinch bolts and axle. It still wouldn't budge until I raised and lowered it a couple of times then suddenly they collapsed as they should. I'm going to put in the right amount of oil and adjust the axle and pinch bolts a little at a time working the tubes up and down to eliminate any binding that may have occurred in the past that has been causing this very rough ride. Thanks again for the pinch bolt tip. I was really not into pulling the wheel and trying to move the tubes one at a time as the fender, bumper, calipers, disk covers all have to be removed and are a pain getting all realigned.

 

Dick

[stardbog]

Huh after this schock / spring elaborat, I Think this thread should end in Tech Library,

 

And Squeeze is well deserv another award,

 

My Vote For Squeeze:080402gudl_prv:

[Squeeze]

Dick, you can't adjust anything by the Torque on the Axle. The Axle has to real tight, because if not, the whole Bearing Assembly doesn't work as it should.

 

If you find it Binding again, you should (eventually) put a thin Washer between right Side Wheel Collar and Forkleg. Just to make sure that the the Torque of the Axle is right and it doesn't cause the Binding again.

[Rocket]

The legs look fully extended, they won't collapse. I don't have the wheel off. I did lossen the Super Brace as the directions that came with the Progressive springs says this is a major cause of forks not operating correctly. I will go out right now and loosen the pinch bolt and see if this has any affect.

 

Thanks, Dick

 

I'm wondering, about the possibility, of bent fork tubes. Hopefully not though.

[Gearhead]

A week or so ago I put in new Progressive springs even though upon measuring I found that my old ones weren't bad.

 

 

Dick, did you get everything torqued down and maintain smooth movement?

 

I found the stock springs in both my Virago and my Venture measured within spec when I replaced them. They had both been bottoming out, however. I don't understand how the springs could get "tired" without becoming shorter (squished, plastic deformation). All steel has basically the same modulus if elasticity (stiffness), from cheap grade to high strength. Different ultimate strength, but same stiffness. This leads me to conclude that either 1) the springs fatigue without getting shorter by some mechanism I don't understand, or 2) they were too weak to begin with. I'm inclined to believe number 2. When we first buy the bike, maybe we ride it gently for a while, not creating the bottoming condition but enjoying the supple ride supplied by the soft springs. Later as we become more confident on the machine, we push it a little harder and, presto, it bottoms out.

 

My point is, just because the springs measure OK doesn't mean they really are strong enough for the bike.

 

Jeremy

[rhncue]

Dick, did you get everything torqued down and maintain smooth movement?

 

I found the stock springs in both my Virago and my Venture measured within spec when I replaced them. They had both been bottoming out, however. I don't understand how the springs could get "tired" without becoming shorter (squished, plastic deformation). All steel has basically the same modulus if elasticity (stiffness), from cheap grade to high strength. Different ultimate strength, but same stiffness. This leads me to conclude that either 1) the springs fatigue without getting shorter by some mechanism I don't understand, or 2) they were too weak to begin with. I'm inclined to believe number 2. When we first buy the bike, maybe we ride it gently for a while, not creating the bottoming condition but enjoying the supple ride supplied by the soft springs. Later as we become more confident on the machine, we push it a little harder and, presto, it bottoms out.

 

My point is, just because the springs measure OK doesn't mean they really are strong enough for the bike.

 

Jeremy

 

I already had Progressive springs in the tubes. I put them in around 2000 or 2001. I thought that they had wore so I ordered new ones without checking the oil in the tubes. When I went to replace them I found one side low on oil and the other side almost empty. This was my real problem. I went ahead and put the new ones in anyway even though the set that was in the tubes were not damaged.

 

My rear mono-shock holds no air and it's spring is shot. it bottoms out constantly and probably my biggest problem as far as the rough ride goes. I rode the bike for about a 100 miles last night trying to determine if it is the front or back that feels so rough. I got a new Progressive spring for the rear but I haven't had time to put it in. I'm hoping that it makes a big difference once I get it installed.

 

Dick

[noworriespete]

My rear mono-shock holds no air and it's spring is shot. it bottoms out constantly and probably my biggest problem as far as the rough ride goes. I rode the bike for about a 100 miles last night trying to determine if it is the front or back that feels so rough. I got a new Progressive spring for the rear but I haven't had time to put it in. I'm hoping that it makes a big difference once I get it installed.

 

Dick

 

I have two things... Dick, I have a rear monoshock that I recieved when I bought my bike... I have been debating if I should save it or sell it.

 

The other thing a painful newbie question... sorry everyone... I'm being told that the seal is going on my front forks because little bit of oil coming out the top. It doesnt sound terribly hard to fix, but I am a poor college student that would like a cheap way to "make it work" forever. Is there a way, and if not, where can I get seals?