Fork Oil Height - The saga continues...

[KIC]

Okay.. as most know I just finished the overhaul of my front forks including the installation of Progressives ( man, are they worth it !!) . I had a question about the fork oil and from what I was told there was 2 ways to determine the "amount" of oil. First was the amount of 409cc's or 13 1/2 oz. The second, was 5 1/2 -inches from the top.

 

The 5 1/2 inches was what most threads stated and what the instructions stated. That is what I installed the oil to. It was way more than 409cc's.

 

Now, yesterday we installed Progressives in my friend's 83. We measured and installed 409cc's in each tube. They were not even, even close to even. So we pumped the lowers and then remeasured and the levels were even but not to 5 1/2 inches, more like 6 1/2+ inches below the top.

 

Now, we read the manual, the threads, the Progressive instructions, and all though they all state to "pump the lowers to extract the old fluid, none state to pump the air out to measure the new fluid. It was obvious that when we installed his oil, air bubbles must have affected the 5 1/2 inch reading and leveled it out after pumping the air out.

 

None of the info we could read, stated what the level from the top should be once they are "pumped" For example, if you just wanted to check you levels of existing oil, to what level should the oil be at from the top ??

 

It seems that there should be a level statement as to before pumping and after. I had the same issue of non level measurements when I poured in my oil before pumping the lowers. It probably took about 15 + oz to level mine out to 5 1/2 inches below. We left his at 6 1/2 inches below with the original 409cc's.

 

 

So what am I missing here ?

Edited May 6, 2016 by KIC

[dingy]

Attached is a PDF of the progressive instructions.

 

I would have to think that the 5 1/2" measurement would be with the system void of air.

 

Also note instructions say this is a Maximum oil level. In the diagram on lower left of 1st page it indicates that below 5 1/2" is a safe oil level.

 

Oil level in shocks isn't like oil in a crankcase, the forks aren't going to run dry if you are at 7 1/2" level. IMHO it is important that they be at the same level somewhere from 5 1/2" to 7 1/2" from top of tube. No springs in tubes & forks completely compressed.

 

The air that is pumped into top of tubes will act like a buffer. Actually the larger the air pocket there is in there, the more even the compression rate will be over the range. Now someone will soon reply that they don't put any air in theirs with progressives and this may be true in that no extra PSI's are added, but there is air in there that acts like a buffer. As the fork moves up, this air pocket increases in pressure, thus restricting the further collapse of the tubes.

 

Gary

Edited March 13, 2012 by dingy
clarified air pocket statement

[MiCarl]

 

The air that is pumped into top of tubes will act like a buffer. Actually the more air there is in there, the more even the compression rate will be over the range. Now someone will soon reply that they don't put any air in theirs with progressives and this may be true in that no extra PSI's are added, but there is air in there that acts like a buffer. As the fork moves up, this air pocket increases in pressure, thus restricting the further collapse of the tubes.

 

Gary

 

Yep. That air trapped at top is like having an additional spring. Less air=stiffer, more=softer.

 

Some forks specify an oil level range so you can tweak the spring rate. Not necessary with air assist.

[Yammer Dan]

A lot have said they run No air with Progressives but I run 4 to 7 lb in mine. Just makes me feel better??

[cabreco]

Bill,

Skydoc explained this to me as follows:

The forks are cast parts not machined so they are not all identical. Imperfections will cause the the +/- fluid level issues.

[KIC]

Thanks. The issue that I was trying to throw out was that I could not find anything that actually stated whether or not to pump the air out of the forks "after" putting in the fluid and measuring. Couldn't find something that matched the 409cc VS the 5 1/2-inch with the air pumped or not. It seems that there should be a statement that states

 

Install 409cc's of fluid that should measure 5 1/2 inches from the top. Bleed air by pumping the lower shocks then measure again with the measurements being ??? from the top.

 

It wasn't just me, there were three of us and one was even a 2nd Gen owner...

[MiCarl]

Thanks. The issue that I was trying to throw out was that I could not find anything that actually stated whether or not to pump the air out of the forks "after" putting in the fluid and measuring. Couldn't find something that matched the 409cc VS the 5 1/2-inch with the air pumped or not. It seems that there should be a statement that states

 

Install 409cc's of fluid that should measure 5 1/2 inches from the top. Bleed air by pumping the lower shocks then measure again with the measurements being ??? from the top.

 

It wasn't just me, there were three of us and one was even a 2nd Gen owner...

 

You pump the air out before measuring. I think it's in the service manual, but not sure.

 

What you're really trying to measure is the amount of air in the forks. You want it to be the same so the spring rate is the same on both sides. If there is air hidden down in the fork measuring from the top won't tell you how much air you have in the system.

 

When you put the spring in the volume of air is reduced by the volume of the spring. That's why you might need to start with more air (lower fluid level) if you're putting in a spring that displaces more volume than a stock spring.

 

A fork that's been in service shouldn't have any trapped air. The correct oil level is the same you start out with on the initial fill.

[twigg]

It's worth noting that Progressive Springs can be installed either way up ... From a spring point of view it doesn't matter.

 

However, it does affect the oil level ... More will be displaced if they are installed "closed coil" down.

[Rick Butler]

WK,

 

You didn't say specifically, but you do realize that the measurement of the oil from the top of the fork tube is without the springs and with the forks completely collapsed. And I think Progressive suggests 5" from the top. The best way to do this is with a turkey baster (that glass tube with the bulb at the top). Measure 5" up from the bottom of the baster tube and put a wrap of painter's tape. Now pour the oil into the fork (with the top tube bottomed out) until it gets close to what you think is a bit more than 5". Then stick the baster into the fork with the tape lined up with the top of the fork and suck out the excess fluid (when you feel the bulb sucking air).

 

Hope this helped,

 

Rick

 

 

Okay.. as most know I just finished the overhaul of my front forks including the installation of Progressives ( man, are they worth it !!) . I had a question about the fork oil and from what I was told there was 2 ways to determine the "amount" of oil. First was the amount of 409cc's or 13 1/2 oz. The second, was 5 1/2 -inches fron the top.

 

The 5 1/2 inches was what most threads stated and what the instructions stated. That is what I installed the oil to. It was way more than 409cc's.

 

Now, yesterday we installe Progressives in my friend's 83. We measured and installed 409cc's in each tube. They were not even, even close to even. So we pumped the lowers and then remeasured and the levels were even but not to 5 1/2 inches, more like 6 1/2+ inches below the top.

 

Now, we read the manual, the threads, the Progressive instructions, and all though they all state to "pump the lowers to extract the old fluid, none state to pump the air out to measure the new fluid. It was obvious that when we installed his oil, air bubbles must have affected the 5 1/2 inch reading and leveled it out after pumping the air out.

 

None of the info we could read, stated what the level from the top should be once they are "pumped" For example, if you just wanted to check you levels of exisitng oil, to what level should the oil be at from the top ??

 

It seems that there should be a level statement as to before pumping and after. I had the same issue of non level measurements when I poured in my oil before pumping the lowers. It probably took about 15 + oz to level mine out to 5 1/2 inches below. We left his at 6 1/2 inches below with the original 409cc's.

 

 

So what amn I missing here ?

[cabreco]

Thanks. The issue that I was trying to throw out was that I could not find anything that actually stated whether or not to pump the air out of the forks "after" putting in the fluid and measuring.

 

 

I can answer that (imagine a newbie with an answer) hen I went to the dealer to get fork oil. I spoke to the service tech about the procedure. He said:

 

"compress the fork, fill he tubes (although he said 409cc he specifically said 5 1/2" from the top) then pump the tubes 5 or 6 time to fill the dampeners. Compress the forks & re measure the level. Expand the forks & install the springs.

[KIC]

WK,

 

You didn't say specifically, but you do realize that the measurement of the oil from the top of the fork tube is without the springs and with the forks completely collapsed. And I think Progressive suggests 5" from the top. The best way to do this is with a turkey baster (that glass tube with the bulb at the top). Measure 5" up from the bottom of the baster tube and put a wrap of painter's tape. Now pour the oil into the fork (with the top tube bottomed out) until it gets close to what you think is a bit more than 5". Then stick the baster into the fork with the tape lined up with the top of the fork and suck out the excess fluid (when you feel the bulb sucking air).

 

Hope this helped, Rick

 

Thanks. I did have the forks collapsed. It is a good idea with the baster.. I used a measuring device I made and a brake vacuum bleeder to "remove" if needed. The baster is an easier device. Everything I have read, and been told, is 5 1/2 inches from top.

 

It's worth noting that Progressive Springs can be installed either way up ... From a spring point of view it doesn't matter.

 

However, it does affect the oil level ... More will be displaced if they are installed "closed coil" down.

 

GOOD POINT !! Although the measurement is with the springs removed.

 

You pump the air out before measuring. I think it's in the service manual, but not sure.

 

A fork that's been in service shouldn't have any trapped air. The correct oil level is the same you start out with on the initial fill.

 

I agree this should be the standard. The fluid appears to be able to leak down into the lower forks while filling , giving different measurements until they are pumped and bled for air. We read our manuals...they state to pump/bleed the lowers to REMOVE old oil, none stated to pump prior to measuring...even the Progressive directions ( we both had the same page that came with the springs.. did not say to pump/bleed AFTER the fluid install. Which brings me to my original thought/question..

 

 

Okay...but my original, $64,000.00 question is...what should the measurement be AFTER you pump out the air and re- measure the fluid ? The main point I am trying to make is once I installed the 409cc it wasn't near the 5 1/2 inches. So I filled to 5 1/2 inches in equal measurements to each side. once one side got to 5 1/2 inches, neither side was equal in measurement. Once pumped for air, I was able to get both sides to 5 1/2 inches. So there must be "draining" down into the tubes as you fill that varies from fork side to side.

 

In order to get it to 5 1/2 inches AFTER pumping the air, I used about 444cc's or approximately 15 oz compared to the recommended 409 cc/ 13.5 oz.

 

In the 83 we did Saturday, the owner just installed the 409 cc's which was close to the 5 1/2 inches but not equal on both sides. Once pumped they both equalized but at a little over 6 1/2 inches from the top.

 

I am just curious as to the discrepancy in the total amounts an the final amount it should be at AFTER pumping the air out.

 

Remember... I am an Investigator... always looking for the clear, correct answer...

[dingy]

Okay...but my original, $64,000.00 question is...what should the measurement be AFTER you pump out the air and re- measure the fluid ? The main point I am trying to make is once I installed the 409cc it wasn't near the 5 1/2 inches. So I filled to 5 1/2 inches in equal measurements to each side. once one side got to 5 1/2 inches, neither side was equal in measurement. Once pumped for air, I was able to get both sides to 5 1/2 inches. So there must be "draining" down into the tubes as you fill that varies from fork side to side.

 

In order to get it to 5 1/2 inches AFTER pumping the air, I used about 444cc's or approximately 15 oz compared to the recommended 409 cc/ 13.5 oz.

 

In the 83 we did Saturday, the owner just installed the 409 cc's which was close to the 5 1/2 inches but not equal on both sides. Once pumped they both equalized but at a little over 6 1/2 inches from the top.

 

I am just curious as to the discrepancy in the total amounts an the final amount it should be at AFTER pumping the air out.

 

Remember... I am an Investigator... always looking for the clear, correct answer...

 

 

Maybe I can help with your fixation on the 409 cc's part. It is meaningless. There are differences in the upper & lower fork tubes from an MKI to an early MKII to a late MKII which will cause this number to vary. This is one of those items that got carried over from the begining of the Ventures history and never got corrected/checked/verified. There are many such things in the service manual/parts fiches.

 

This presents you with a great oppurtunity to hone your investigative skills. After you are satisfied with the 5 1/2" measurement and you have stroked that lower fork tube till your arms are weak to get the air out. Get a scale capable of weighing in grams (Harbor freight has a nice one for under $20). Get a clean container, weigh it, then drain your fork oil into the container. Weigh the now semi filled container again, deduct the empty container weight. Multiply net weight (in grams) x the specific gravity for 10w oil (avg is .93). This number should represent the amount of cc's of the drained oil. Interogate the forks to assertain how much oil is not being forthecoming through the drain hole, add the amount that was not surrendered volintarily and there you have it, simple as that.

 

 

Be sure and post your findings, I am on pins and needles. Plus it took most of my lunch to type this.

 

Gary

Edited March 13, 2012 by dingy
spelling

[twigg]

Or ya could just fill the tubes, compressed .. get the air out and set the level at 5 1/2" ... and quit worrying about it

[KIC]

Or ya could just fill the tubes, compressed .. get the air out and set the level at 5 1/2" ... and quit worrying about it

 

 

 

But, that wouldn't answer my question....

Edited March 13, 2012 by KIC

[cabreco]

Or ya could just fill the tubes, compressed .. get the air out and set the level at 5 1/2" ... and quit worrying about it

 

 

Man Bill, and I thought I was OCD?

 

We have a saying here in Virginia..."It is what it is". Let it go man...calm...shhh shh, it's all good. http://www.smileyvault.com/albums/CBSA/thumb_smileyvault-cute-big-smiley-animated-049.gif (LOL)

[KIC]

Man Bill, and I thought I was OCD?

 

We have a saying here in Virginia..."It is what it is". Let it go man...calm...shhh shh, it's all good. http://www.smileyvault.com/albums/CBSA/thumb_smileyvault-cute-big-smiley-animated-049.gif (LOL)

 

 

Yea,, I agree,,,since I can't seem to get a solid answer anyways... so what do you think ??

 

Before ?? After ??

 

 

[cabreco]

Yea,, I agree,,,since I can't seem to get a solid answer anyways... so what do you think ??

Before ?? After ??

 

The solid answer is after! (according to the Yamaha dealership service tech)

I asked, ok now you can S L E E P.. http://i625.photobucket.com/albums/tt335/bjtilt/th_Smiley-sleeping.gif(LOL)

[a1bummer]

WK,

 

You didn't say specifically, but you do realize that the measurement of the oil from the top of the fork tube is without the springs and with the forks completely collapsed. And I think Progressive suggests 5" from the top. The best way to do this is with a turkey baster (that glass tube with the bulb at the top). Measure 5" up from the bottom of the baster tube and put a wrap of painter's tape. Now pour the oil into the fork (with the top tube bottomed out) until it gets close to what you think is a bit more than 5". Then stick the baster into the fork with the tape lined up with the top of the fork and suck out the excess fluid (when you feel the bulb sucking air).

 

Hope this helped,

 

Rick

 

What he said. Here is a tool that is made specifically for the job.

http://www.jakewilson.com/p/53/-/392/754/-/10975/Tusk-Fork-Oil-Level-Tool/FORK+OIL+SYRINGE

 

Bill

[KIC]

What he said. Here is a tool that is made specifically for the job.

http://www.jakewilson.com/p/53/-/392/754/-/10975/Tusk-Fork-Oil-Level-Tool/FORK+OIL+SYRINGE

 

Bill

 

You know..you just gave me an idea. I have, and used, my suction brake bleeder. All I have to do is make the adjustable piece to lay across the fork tube opening and it would easily do the same thing.

 

Thanks

[GolfVenture]

Glad I found this. I'm ready to begin the install procedure this morning.

 

Also thanks for the talk yesterday KIC.

[cabreco]

Glad I found this. I'm ready to begin the install procedure this morning.

 

 

Brian this install is really way too easy! If you take it super slow, you be done in 2 hours.

Although it makes no difference in performance which way you install the springs, installing them tight coils down cuts down on noise.

I also didn't use the supplied washers. I took the OEM ones & inverted them around the PCV spacer. The OEMs have a lip so they won't move when installing the fork cap.

[KIC]

Brian..you know our motto here... To Serve and Confuse.