my clutch has never been smoother than it is with atf, I have a local shop that helps me with stuff I don't think I can do and he has used atf for years, I was a little skeptical at first but I like it

 

Not on mine you can't!

 

20w 50w v line 4 stroke dino in all 3 holes... change engine every 2 to 3...

 

Mobil 1 synthetic ATF.

ATF is a waste of money? I blew $22k on a motorcycle that is used strictly for fun.

 

10w40. Pretty sure that was standard before HD syn3 and all these "chaincase/primary" specialty products. I use Amsoil motorcycle synthetic; obviously opinions vary re synthetic or conventional but what I would NOT do is run standard automotive synthetics as I was given to understand they can cause issues with wet clutches while motorcycle synthetics should not. For conventional oil I would run a diesel version for same reason, though would likely be a 15w40 in that case. I would likewise avoid running "gear" oils in primary, 80w90 and such, as they have other additives designed for transmissions/differentials. I've also heard of heavy gear oils causing issues in older chain driven transfer cases on 4wd pickups that specified 10w40 engine oil, and while it seems unlikely to be a problem at temps we ride bikes I don't see the point risking it.

 

You may want to think about this too. Although the primary doesn't generate much heat in and of itself that's not the only concern when choosing a fluid.
The primary on your motorcycle is not a seperate entity. It is attached to the engine and it acts as a giant heatsink for that engine. [/QUOTE]

100% correct of the primary acting as a heatsink. After a good ride in hot weather, when I come to a atop I can't even lean my left leg against the derby cover. There's a lot of heat going on in there and that's the reason why I run a 100% PAO Ester 10W-40 JASO rated motorcycle oil in there. Synthetics handle the heat better no matter what weight of oil you're using.

 

100% correct of the primary acting as a heatsink. After a good ride in hot weather, when I come to a atop I can't even lean my left leg against the derby cover. There's a lot of heat going on in there and that's the reason why I run a 100% PAO Ester 10W-40 JASO rated motorcycle oil in there. Synthetics handle the heat better no matter what weight of oil you're using.[/QUOTE]
I think that has gotten worse with emissions and bigger engines. My 103HO is not as bad as my 2007. My 95" not as bad, and I don't recall it being that bad when stock 88.

as for fluid, I really don't know if it matters, in any of the holes. For years I ran with syn3 in all 3 holes. Then I tried red line. Then Harley mechanic got me to change to belray. I am not sure big difference. Tried it one of my primaries. Not sure a difference.