Fork oil weight

[dave04kdx]

Hey All

It's been a while but I'm getting the 04 KDX ready to ride when it's a bit cooler here. I'm going to service my stock forks tonight and planned on getting some oil on the way home from work. I can't remember what weight oil to use. Anyone know off the top of their head?

Thanks

David

[KarlP]

I liked a 50/50 mix of 5 and 10 wght fork oil.

Fredette likes the Golden Spectro cartridge fork oil. I used it on one change and thought it was good, but hard to find.

Lots of people use ATF. My forks aren't an Automatic Transmission, so I always used Fork Oil

[dave04kdx]

Cool, thanks for the heads up Karl. I'll try the 50/50 mix and see how she feels.

[canyncarvr]

Re: 'Anyone know off the top of their head?'

Sounds like you're set..but for a casual passer-by-reader...fork oil weight is going to be a matter of personal preference. In the case of OEM (RSU..meaing NOT USD) forks, rebound action can be effected by changing oil weight..OEM forks have no rebound control..no rebound adjustment.

While some (can you even IMAGINE!!) may guffaw at using ATF in RSUs or USDs, Jeremy Wilkey, MX-Tech, has recommended such (Mobil 1 ATF anyway) for fork at-home-service.

TRUE fork oil..meaning a bottle of stuff that experts might agree once in awhile on using once in awhile...is expensive. Meaning..$30 or more a quart.

I have used Mobil-1 ATF in my forks, both USD and RSU. Mobil rates it at 7.6cST, which I understand to be 'about' a 16-17W. The whole weight classification may well vary from one mfg. to another anyway. That shouldn't happen, of course, but it seems to anyway.

From Mobil:

Typical Properties

Mobil 1 Synthetic ATF

Viscosity, ASTM D 445
cSt @ 40º C 36.3
cSt @ 100º C 7.4
Brookfield Viscosity, ASTM D 5293
-cP @ -40º C 10,040
Viscosity Index, ASTM D 2270 176
Pour Point, ºC, ASTM D 97 -41C
Flash Point, ºC, ASTM D 92 200
Density @15º C kg/l, ASTM D 4052 0.846


An added advantage to using ATF in your forks is a smoother shifting transmission.

Bonus!!



**edit**

Picked this up from TT:

http://www.peterverdonedesigns.com/lowspeed.htm

Take note:

DO NOT GO BY LABLED OIL WEIGHT! Not only is this a poor way to decide which oil to use, but each manufacturer seems to be on a different scale. For example Maxima RSF 7wt is actually lighter than Spectro 5wt and Silkolene Pro RSF 7.5wt is actually heavier than Showa SS-8 10wt. This is not a judgment about the quality of these oils, just that the 'weight' label leads to a lot of trouble when trying to tune with suspension oils.

[OLHILLBILLY]

I used 5wt Maxima in mine and it does seem to be a little light on rebound. Not bad enough to cause me any real problems but I can feel it. When I do them again I believe I'll use the 50-50 mix of 5wt and 10wt to try to get a little more rebound dampening.
And since the Maxima is on the parts store shelf I'll stick with it so I'll have some consistency in my changes.

[KarlP]

"An added advantage to using ATF in your forks is a smoother shifting transmission."

I think the OP might find this confusing.

I don't because I don't use Automatic Transmission Fluid in my non-Automatic Transmission, either.

[canyncarvr]

I dont....

You don't.....what? Find 'this' confusing?

Your non-use of ATF has led to exceedingly excellent clarity of thought?

..my non-Automatic...

My transmission is 'non-' a lot of things.

I don't use coffee beans in my non-bean-grinder transmission.

Dave's (OP) not confused. He knows what success is.

[Colorado Mike]

I used Golden Spectro in my kids YZ last week when I changed the seals. I thought it was a pretty good deal at about $12 per quart, but about 2 days after putting it in, he went and sold the bike.

That crap didn't last long at all.

[OLHILLBILLY]

That ATF sure must be some good stuff. Seems folks is usin it fer everything these days. Gearbox, forks, even use the stuff in those new fangled car transmissions that you just put the lever in one place 'n it does everthing fer ya.
.
.
.
.
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Sorry, I couldn't resist.

[canyncarvr]

That ATF sure must be some good stuff.

Isn't that what you would expect from something called All Things Fluid?

Seems perfectly reasonable to me.

[porterdog]

ATF, shim stack mod, and XR400 springs made this 190lb rider much happier than the stock setup.

[dave04kdx]

I got the oil but didn't get around to changing my fork oil. My son and I worked on his TTR-125L first. His bike had ATF in the forks from the factory. I might try some Mobil 1 ATF in my bike this time and see how it feels. I still have the stock forks with the .40kg Fredette springs.

I forgot how much fun it is to have Carvr answer one of your posts
Very, very informative and entertaining at the same time. Thanks Brad.

David

[canyncarvr]

Re: 'I forgot how much fun it is to have Carvr answer one of your posts..'

I was taking my meds on this one. That's a plus..........

How many riders have the slightest idea what a centistoke is, anyway?

Uh...that is what the 'cSt' stands for in case someone didn't look it up.




Or maybe it's a 100cc bike?



Not that it's the subject of discussion, but some manual transmissions in automobiles use ATF. Such might be referred to as a 'non-automatic' transmission.

So there!

[KarlP]

I know what a centistoke is. It is the hundreth piece of wood or coal you put in a fire.

(ha-ha, made you look)

Years ago I'd use used motor oil on my foam air filter.

Now I use Foam Air Filter Oil on my foam air filter.

Maybe I'll try it in my forks?

[canyncarvr]

I know what a centistoke is. It is the hundreth piece of wood or coal you put in a fire.

(ha-ha, made you look)

Years ago I'd use used motor oil on my foam air filter.

Now I use Foam Air Filter Oil on my foam air filter.

Maybe I'll try it in my forks?

Wow. You got it ALL backwards.

You've heard, perhaps of the term 'Scientific Method'? Lest I be again convicted of mixing up medications, let us query Mr. Google:

Scientific method refers to bodies of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge...

Your experience with used motor oil having been found to be satisfactory for use on a foam filter tells us that it's used motor oil that is the choice for use as fork oil.

Good grief. I've not used 'foam air' IN/ON anything and am unfamiliar with its satisfactory use FOR anything. Seems at best it would render anything it was applied to...well...breathless. Besides, I'm willing to bet the container within which such is contained...in... rather expressly states the contents within to be used specifically for foam filters, NOT forks.

Find THAT caution ANYwhere on your used motor oil container (said container being specifically intended for use as a vessel for such fluid).

Besides, most foam filter oils indicate the proper application to include the instruction to 'remove excess...' by squeezing said excess from the air filter following a too generous application in the first place.

Squeezing your forks in the hope of removing excess oil I don't think will work.

Add sufficient quantity of air foam fork oil to exceed the desired oil level measurement. Squeeze the lower fork tube to vacate the excess oil applied..to reach the desired oil level in the fork tube.

..I don't think so.


Whew! Another internet myth blasted to hell and gone..........

[KarlP]

Is all I got to say

[lemmy]

Ie I'll use the 50-50 mix of 5wt and 10wt to try to get a little more rebound dampening.

try pouring water in, that might "dampen" your rebound :)

[canyncarvr]

OH NO!!!....not the damping/dampening argument!!!


I'll bet Dave is sorry he started all this..................


Maybe the problem in the rebound is that it IS damp to start with. Maybe from using oil from a not-quite-well-sealed-enough container? We all know the hygroscopic tendencies of fork oil! Can you put one'a those little desiccant bags of 'WARNING!! Do Not Eat!' inside the fork tube to take care of that?

[KarlP]

No, no, no

The dampness comes from not wringing out the lower fork leg. Everybody knows that, don't confuse Dave any more.

Poor guy is already expecting a smoother shifting transmission on his KDX becauase he changed the fork oil in his boys TTR.

[dave04kdx]

I'll bet Dave is sorry he started all this..................


I already knew the anwser to the fork oil question. It's just been too hot here to ride and I was bored...... My next posts will likely consist of some jetting questions, how many holes to drill in the air box questions, which graphics look best and lastly how the KDX compares to a KX 250 when jumping

Seriously, thanks to all for the info.

David