Jump to content
Sign in to follow this  

Front Forks / Dumb question time

Recommended Posts

OK, may be dumb question time.

I'm doing my year end maintenance on the bikes and figured after three years, I should change the fork oil out. My seals are fine and I don't plan on changing the damper oil (inner chamber).

Here's the question: the manual shows draining the fork assembly with the damper assembly removed; do I really need to removing it?

Seems like I could just leave the fork leg upside down for a bit or will doing so with the damper assembly in the leg possibly drain oil from the damper as well?

And how long should I leave it inverted? The manual has this chart with temp vs time and how much oil will be left in the leg.

That seems a little crazy. I'm just thinking of leaving them inverted over night and then filling them back up with the recommended amount of 11 oz of oil.

Jim.

Share this post


Link to post
Share on other sites

The reason they want it removed is so you can properly drain and blow out any oil that comes out of the 2 weep/transfer holes in the cartridge assembly , you need to tip it so the hole is down , and drain and tip it back and forth then blow out with air any oil left in there , you can do away with the sitting time by simply putting a clean *lint free* rag (once the forks are apart as the manual states) and use a broom handle to push the rag thru removing all the oil , you can do the same to the lower legs , but you need a wire or string attached to the rag so you can retrieve it , this will eliminate the "waiting" period , and is how i do mine when i am not wanting to sit around watching the oil drip out forever when i am re-valving , as it comes apart , then goes together , then comes apart , it gets old having to wait

This is all to ensure that when you replace the oil it will be the proper amount , because of residual oil left in everything , if you did not get all the oil out you could have 10 or more cc's of oil difference per side which would affect balance of the 2 forks when riding

It would be the same effect as having the clickers different from side to side

Share this post


Link to post
Share on other sites

You really need to set the oil height and not just add 10oz. You can adj. the height with a meat baster and a small hose or buy one of the high dollar tools to do it with.

Share this post


Link to post
Share on other sites
You really need to set the oil height and not just add 10oz. You can adj. the height with a meat baster and a small hose or buy one of the high dollar tools to do it with.

Where do you find a height spec? When I did my seals I could not find one and had to go by the manual.

Share this post


Link to post
Share on other sites
Where do you find a height spec? When I did my seals I could not find one and had to go by the manual.

Only height spec I saw in the manual was for the damper assy and a video iwatched today didn't even bother with that. They just filled the damper chamber to the bleed holes and then inserted the cartrige slowly. For the outer chamber, no height was specified in the manual. Just x oz of oil.

Jim

Share this post


Link to post
Share on other sites
Only height spec I saw in the manual was for the damper assy and a video iwatched today didn't even bother with that. They just filled the damper chamber to the bleed holes and then inserted the cartrige slowly. For the outer chamber, no height was specified in the manual. Just x oz of oil.

Jim

I thought it was in a factory service manual. I set mine 110mm from the top with the fork bottomed out. 5 mm more or less will change the bottom out rate.

Share this post


Link to post
Share on other sites

That is one of the threads I saw yesterday and when he fills the fork leg tube, he just dumps in 370 ml of oil.

Here's the links for the video's I saw, which I thought were pretty good:

Part 1:

Part 2:

Part 3:

Part 3 has the section where when changing the damper oil, he doesn't bother to check the height in the tube, but simply fills it to the bleed holes and then puts in the cartrige slowly after pumping the damper rod several times.

I did BTW find the answer to my question. I noticed last night that on the competition maintenance schedule, fork oil and damper oil are shown as two seperate services and the fork oil change alone is covered in a seperate section of the manual. What was a bit confusing was the section that included the damper oil (which I originally found first) had both changing the fork oil and damper oil in it and here, it shows draining the fork oil with the damper assembly removed.

The first section however shows that the fork oil can be drained with the damper assembly being left in the tube. I'm going to leave them inverted about 3 hours, which should leave .1 - .2 oz left in the tube and then fill with 10.9 oz. That should get me pretty darn close the original and for a rider like me, I doubt I'll notice the difference.

Thanks for all the responses.

Jim.

Share this post


Link to post
Share on other sites

Jim,

the fork oil in the outer tube can be successfully drained while leaving the cartridge in place. However, the fluid inside the cartridge is the fluid that really needs replacing. It's the fluid that actually does the work.

The fluid in the outer chamber merely serves to lube the bushings and fine tune the air pocket.

Share this post


Link to post
Share on other sites
Jim,

the fork oil in the outer tube can be successfully drained while leaving the cartridge in place. However, the fluid inside the cartridge is the fluid that really needs replacing. It's the fluid that actually does the work.

The fluid in the outer chamber merely serves to lube the bushings and fine tune the air pocket.

Hum...it takes care of compression doesn't it? But in any case, it's also the one that's prone to the most contamination. The damper is a sealed unit, where as the fork oil will pick up anything that makes it past the seals.

I should mention that I am by no means a hard rider (I'm 51) doing mostly trail riding and 3 or 4 HS a year, and I split my time between two bikes to boot. However when trail riding, I've had both bikes up to the tank in water. So I was more concerned about the fork oil. I wash the bikes after every ride and am very carefull to clean the tubes off and dry them fully, but even so, after three years, I figured it would be a good idea to change the fork oil out.

Based on my ridding, I figure I'm closer to the non-competition maintenance schedule, which doesn't call for fork or damper oil changes at all for the first 2400 miles. Right now both bikes have a little over 400 miles on them.

The competition schedule calls for a fork oil change after 7.5 hours and damper oil at 22.5, but I've ridden neither that hard and am really not concerned about the damper oil.

Jim.

Share this post


Link to post
Share on other sites

The outer chamber does not control compression. That's a function of both the base and mid valves. They are in the cartridge.

The fluid in the outer chamber does nothing more than lube the bushings and adjust the air pocket. The air pocket can account for increased stiffness if it becomes pressurized or if the fluid is overfilled. Stiffness is not a component of compression damping.

The fine tuning of the air pocket can be used to aid in bottoming resistance.

Bottom line is the whale oil that Honda puts in there from the factory is horrible and should be changed as soon as possible, in both chambers.

The oil in the cartridge gets contaminated by the wearing of the bushings and gets broken down by the shearing forces as it goes through the valving. It is the fluid that really needs replacement.

Share this post


Link to post
Share on other sites
The outer chamber does not control compression. That's a function of both the base and mid valves. They are in the cartridge.

The fluid in the outer chamber does nothing more than lube the bushings and adjust the air pocket. The air pocket can account for increased stiffness if it becomes pressurized or if the fluid is overfilled. Stiffness is not a component of compression damping.

The fine tuning of the air pocket can be used to aid in bottoming resistance.

Bottom line is the whale oil that Honda puts in there from the factory is horrible and should be changed as soon as possible, in both chambers.

The oil in the cartridge gets contaminated by the wearing of the bushings and gets broken down by the shearing forces as it goes through the valving. It is the fluid that really needs replacement.

All this is true. The fine tuning of the air pocket is why I posted my early post. I understand that you don't want to do more work than you think you need to do. So if you change all the oil or just the outer you need to set the oil hight with a measurement and not just pour in a fluid amount measured in oz.

Good Luck with it. :lol:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×