Textbook recommends Fork OIl change annually. You?

[sgtslag]

I was doing some 'lite' reading in my textbook, Motorcycles:  Fundamentals, Service, Repair, Copyright 1999, and I re-discovered where it states:  "Even under the most ideal conditions, the fork oil should be changed at least once a year."

I used Dexron IV ATF (conventional), in my Voyager, and my CB, with decent results (it's only $5-$7 per quart, ~8 wt. viscosity; Fork Oil is usually around $15 per quart!).  Last year, I changed out my fluid in my Voyager, after it had been in use for two years:  I added an ounce of SeaFoam, first, pumped the wheel up/down 20 times, to percolate it through the system, dissolving varnish, gum, etc., before I drained it.  The fluid came out a duller red, no particles, just duller in color than it was, originally.  I then poured in some Dexron VI Synthetic ATF (around $7 per quart; being a full synthetic oil, it should last twice as long, or two years).  I am on the fence whether I should drain it this Spring, if only to test it's color/health, to see if I could go two years with it.  It is certainly cheap enough to squander a half-quart to find out.

How long do you go between Fork OIl changes?

[shinyribs]

I'm not sure fork oil or ATF either one will break down in a years time just due to age. I'd say it has more to do with miles ridden than time spent inside the forks. I suppose if you have a leaky fork seal that was allowing moisture in to the system that it could affect the oil quicker, but that's a whole other ball of wax.

Right before I sold my '76 recently I swapped the front end on it. Those forks had fork oil in them and that oil was about 1.5 years old with about 5k miles on it. It had darkened a tad, but it wasn't too bad IMO. And these legs had never been properly flushed. Just a simple drain and refills. But I had been playing with fork oil weights to see what I liked (tried two or three different weights) and riding for just a few days on each test. So it's kinda like it did get flushed out in a way.

I don't have anything against ATF, but being able to ''tune'' your forks with different weight oils is nice. In the end I probably dropped about $60 on various weights of fork oil, but the result was a front end that was really comfortable to me. IMO it's worth the added cost.

[sgtslag]

I hear you, Shiny.  All of the auto-mechanics I talk to, today, still say, "Change the oil in your car/truck every 3,000 miles, or every four months."  Ford, Chrysler, and GM, however, say change it every 5,000-7,000 miles, in modern cars and trucks!  Mechanics seem to think it's still 1970, and we're all running API SF oil, not the current SN oils, that engine designs, and oil production sciences, have not changed in the past 40+ years.

With engine oil changes, the quarterly interval was based on acid byproducts from combustion, breaking the oil down, over time.  What they ignore, is that motor oil is made with bases added, to counter-act the acid build-up.  The idea of needing to change it based on time, is bogus to me.
With regards to tuning the suspension, I agree, it can be a worthwhile effort, though it can get expensive.  I tried 15 wt. fork oil, in my Voyager, based on forum recommendations.  I did not like it, as it was too harsh.  I went back to the 8 wt. ATF, and I've been happier since (I'd spend the $$ if the Fork Oils gave a better/safer ride).

The textbook was written in 1999, so it is dated, being 15 years old.  It is impossible to tell if the authors were of the 1970's mindset on oil change intervals.  Don't know what modern bike owner's manuals call for on change intervals (my Voyager is 21 years old).

The color change in my fork oil, after two years, might have been because I added clear, motor-treatment SeaFoam to it.  They make a Trans-Tune product, which according to the MSDS, is the same product, but with red dye added to it, and a price tag around $2 higher.  I won't treat the engine, or the forks, with SeaFoam again.  After using SeaFoam on my CB, twice, 5,000 miles apart, and getting no sludge/discoloration the second time, I believe what I washed out with the first treatment, likely came from the SF-rated oil used when the bike was new (1979).  The modern, SN-rated oils, seem to leave almost nothing behind in the way of varnish, and sludge (unless you run it too hot!).

I really wondered if folks actually service their forks on a regular basis.  I suspect it is one of the most neglected maintenance items on all bikes.  The modern ATF's are very high in detergents, compared to the older stuff (Dexron II back in 1979), so that's another reason not to need any cleaner like SeaFoam again.  Not sure if Fork Oil has detergents in it.  For those who haven't changed it in a long while, a cleaner might be a good idea to cleanse the fork's innards, at least once (some folks on the Voyager forums use mineral spirits).

This being Winter, thought I'd bring up a possible maintenance item for folks to think about, come Spring.  Last year, I had completed all of the maintenance items on my bike, and all I had to do, was ride it.  It was a bit strange not working on it to change out this, or replace that.  I kind of missed the wrenching.  Next year looks to be more of the same...  Cheers!

[TOOLS1]

After 9K miles I changed my fork oil (ATF), and it had turned dark, but not as bad as the Goo I drained out at 19K.
TOOLS

[sgtslag]

The first time I changed mine in my Honda, shortly after I bought it, it came out a dark Green color.  No idea if it was fork oil, or ATF (no idea when/if it had ever been changed in its then-27 year life).  Whatever it was, it was past its prime.

[SoonerRon]

35 year old fork oil has got to be one of the nastiest smelling substances known to man.

[TOOLS1]

SoonerRon wrote

35 year old fork oil has got to be one of the nastiest smelling substances known to man.

Toolmut even smells better.
TOOLS