ATF in Forks?

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I love all the genius responses here that say don't use ATF in motorcycle forks. Have a look at the official Honda service manual for one of my old bikes, see the "specified fluid"?
 
Maybe to clarify, plus I do find this a fun topic......it looks like some of you guys are thinking of the term "ATF" as if it means a particular weight or has some other property that either is compatible with the forks inner workings or destructive to them. It doesn't. As a couple of folks have mentioned, fork action is primarily about the weight of the fluid, that's what's going to dictate if it makes your forks feel good for your forks and conditions. Whether it be ATF, fork oil, motor oil, hydraulic oil, whatever, it comes down to the weight. "ATF" if just a convenient label that gets thrown around, but it comes in all different weights just like fork oil. Doesn't mean a whole lot by itself other than it's probably going to be somewhere around 8 cSt at 100C of it's a Dex III equivalent or or 5 if it's the LV variety. No different than your "proper" fork oils coming in 5w, 10w, 15w, whatever.

Back to the OP question of can he use ATF for normal street riding with an avg size rider? Yes, nothing bad will happen. Period. Will it be the best feel? Maybe, it depends on your forks and what you consider "good". You never know until to try it. If the action is too stiff or wallowy, go to a lighter or heavier weight oil. But look at the viscosity specs, the printed weight on the bottle doesn't mean a whole lot unfortunately. M1 ATF is great stuff, I use it in forks and shocks, but it only works great when the viscosity matches up with the above. I can tell you it's almost identical to Honda/Showa SS8, if that appeals to you.
 
BTW, I'd start with the question of if your forks are cartridge forks or damper rod forks. Damper rods generally like something a little heavier than cartridges, but that's a feel thing, not a "it's gonna seize" thing.
 
How about this, motorcycle is 2000 Honda VFR800 and I have all of these type of ATF's laying around. Now which one it would be?


 
Try it and see (any of them) ... It's not rocket science. There are two volumes usually listed in the service manuals. There is the dry re-fill volume as in the forks were completely apart, have been reassembled and need to be refilled. And there is the service volume for forks that have only been drained on the bike.

Use a measuring cup, or graduated cylinder and capture each fork leg when you pull the drain plug. Remember to pump the front end up and down a few times while draining. Do it slowly, but work it some. That measure should be the service volume ... Check it against the book. Prolly do not want to add too much more than that when refilling.

We also used to do the 6" thing. Six inches down from the top of the fork when compressed, no spring is the service fill for forks we did not have the manual for. Extended and with spring inserted, they'd usually ride pretty well. Had enough air in the top to not blow seals on a hard bump that hit the stops
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Race bike were a whole nuther can of worms. Mostly it depended on if air caps were fitted, what kind of seals were installed, etc. We'd vary the fluid level to dial in the exponential pressure rise in the air column to get that last bit of usable wheel travel with a good stroke stop. You are on your own developing that volume ...
 
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