I had a thought the other day and am going to try it and see if there is any noticeable difference but until then I thought I would throw it out as a
thought
The thought consists of since the forks tube system is a sealed system which means there is no fluid being allowed to leak out of the various areas...
Would this also mean its sealed off to air getting in/out as well?
One remark was when I was talking to Traxxion they offer a tool that will help remove all the air in the forks...
So if a tool will help remove air in the forks then would it be safe to say none can get in/out as well????

Years ago HD offered a front end that was air assist...It seemed to be along the same design as the conventional front forks are with the exception
of the large bolt on top and the bolt under the top tree it appeared it was the same...Even so with the newer forks design it should be along the
same theory without the added feature of being able to add air...

Assuming if they are self sealed and no air can get in or out
then when we change out fluids on the front end on the preventative maintenance and choose not to take the forks apart and just drain and dump
the measured amount then would it make a difference as to whether the forks were fully extended when the large nut it wrenched back on
VS.
when the front forks had the entire weight of the bike on it and wrenched on the large nut on top of the tree...

theory here is if the forks were fully extended there would be air trapped inside the tube assy. and would give a different feel
(Kinda like having a air assist front end with out the option of being able to put air in it...)
VS.
Forks compressed with not the volume of air???
VS.
should we trying to achieve the removal of all the air in the cavity of the tube
FFT
paul

 

Without beating a dead horse, if you do not take the fork completely apart and clean it spotless, replace the bushings, replace the damper piston rings as per manual, polish the fork tubes, apply a protective coating that is also slippery, inspect all for wear, than put it all back together.

I have had local HDF Members come over and I guided them, using my shop and tools, to R&R their forks as I took pictures. They posted their findings and I supplied and hosted the pictures for ease of explanation and evidence.

1. Your fork oil is not cooled or is it filtered.
2. When your forks go up or down the fork springs are rubbing against the inside of the fork tubes continually making a fine metal powder. Some of his powder is suspended in the very same oil that lubricates your fork bushings.
3. Your fork bushings have a Teflon coating on them which makes the forks slide easier. Once the Teflon is worn off just the brass or steel bushing is sliding against the fork tubes.
4. Dirt is washed down past the oil seal on a dresser and winds in the oil.
5. No fork is sealed unless you are using a gas cartridge but the dirty oil and bushings still apply.
6. No matter how many times I try and teach the members here what is inside of the fork and how to rebuild them, the next question is "How do you change the oil without doing any work".

One more time I will post these pictures:

Your HD oil after 5,000+ miles but less than 10K mi:


The metal that was strained out of the oil (just big parts only and no power)



The crap inside of a newer fork slider with less than 10K miles



Just inside of the fork tube once it had been rinsed out thoroughly with solvent than run a swab down the inside of the fork;



I know I am wasting my time but just maybe only one will get the idea;

And lastly this is Amy who volunteered her time to teach you proper maintenance;

 

All forks are air tight. My bike has the air assist system, which still works fine as if ever did. The handlebars are an air reservoir linked via a manifold to the tops of the legs. The air provides additional springing under normal riding conditions, then when the front brake is applied a valve is closed, so only the air in the fork legs can compress. This stiffens the forks up and reduces dive under braking.

That sounds fine, but as a suspension system it is not very good! Harley doens' fit decent suspension, except on occasional models. Howard, who posted above, is developing a superior replacement, using modern cartridge inserts!

I don't see any advantage in removing the air from the front forks. They will still have to be 'air tight' to function and not spraying oil about.

 

Howard
glad to hear your up and about
I understand there is all kind of contaminants in the fluid and they should be over hauled every 50,000 miles or so but for some us we try and keep the fluids in the forks once a year

So my question is there are 2 ways here
1-being when the fluid is in does the bike need to be completely on the pavement before the top big bolt that is on top of the triple tree be installed
or
2- being when the fluid is in does the bike need to be up off the floor to create more room for additional volume of air and then tighten the big bolt on top of the triple tree

What if any advantages would it make is what I'm seeking
paul

 

I too don't believe removing all the air in the forks is the right answer here
so this isn't going to happen
I'm just curious if it's better to put the cap which sits atop the triple tree on and tighten it before the bike is set on the floor there fore increasing the volume of space for air thus increasing the air/fluid volume
or
after compressing the forks with the weight of the bike only decressing the volume of space for air on top of the fluid thus reducing the air/fluid volume
paul

 

#1. Yes
#2.You would be creating a vacuum when the fork fully extended if it were air tight.

 

#2 I don't see near as much if any negative vacuum here
I see more air added on top of the fluid level like the older versions were with air assist...
So there fore when the forks are called upon to extend then the negative vacuum (what little bit might be there if any) would be created...
With this procedure there would not be as much to concern with since most of the tube is fully extended out when the air is trapped inside
this may give the feeling of a bit more firmer front end as opposed to the other method...

#1 However I do see a negative vacuum added with this method now that you mention it...
If the forks bolt cap is tightened when the bike sits on the ground then when the forks extend past THIS OVAL(dimension that are with the bike sitting on the ground) dimension then this would create a negative vacuum...

paul

 

You mean like having an external pump & reservoir on the suspension working like a diaphragm carburetor (weed eater, chain saw, pre-fuelinjected bi-plane) keeping pressure on the fluid, whether in or out, but not letting air into the suspension system itself

 

*The fork is collapsed and spring is out than fill to oil height as per book/manual.


* I understand there is all kind of contaminants in the fluid and they should be over hauled every 50,000 miles or so but for some us we try and keep the fluids in the forks once a year
<<< I am sorry if I do not write clear. 50K miles is way too many and I recommend 7.5K for cartridges & 10K for conventional as there are no shim stacks to get clogged up.


For conventional forks the space between oil and top of the fork is in the manual and that is when the spring (& if you have some sort of emulator) be removed and the slider is all the way up. I do not use volume but oil height. If you wish tp form up the forks you do not put thicker oil but you decrease the "Air Spring" which is the length between the oil and fork cap. Just as in the movie.

When you have air assist or air pressure in the front forks you are doing the same thing as when you raise up the oil level in relation to the fork cap. Read this chart, all of the resistance are achieved by changing the oil level and not by changing viscosity of the oil:

 

Paul,

Having ridden on my air-assist forks from new in 1990 they only become noticable at around 10psi and worthwhile at around 15psi. If the forks are fully extended when sealing them, the pressure inside when the bike is back on its wheels is going to be very small IMHO.