So Riddle Me THIS!

[JD]

Ok, check this out. This may blow your mind. So for the last several years, running some generic wet cluch (Castrol I think) 10w-40 oil in the primary, the inner seal (where the output shaft from the clutch goes out to the tranny) had been leaking. It was ok when sitting cold, but every time I went for a ride it would leave a quarter sized oil drop wherever I stopped. Nothing major, but enough to get your attention. Anyway, last season I switched over to Mobil-1 10w-40 "V-Twin" synthetic. All year not a single drop! It's like the thing fixed itself LOL. And, before you ask, yes, the primary is filled full with oil.

[Rice-out]

Some oils have additives in them that rejuvinate the polymers in the rubber compounds the seals are made of. Where that is a synthetic I would assume it does.

[Wide]

Simple terms the oil sticks to itself providing a film

Cool beans, thanks much for sharing that. I like documented things from experienced people

[JD]

Yes, I understand that some oils have "seal conditioners" but always thought it was more of a preventive thing than a stop leak LOL.

The clutch grabs much smoother to boot

[JD]

Correction...for the Mobil-1 synthetic motorcycle oils, 20w-50 is labeled "V-Twin" whereas the 10w-40 is labeled "Racing" or something along those lines. Whatever it is labeled, I am using the 10w-40 in the primary.

[DutchBiker42]

You should be using a 20w-50 oil. The 10-40 is too thin. Thats why it didn't leak when it was cold,once it warms up it thins out and finds a way to get out. I personally recommend Amsoil 20w-50,not only for the primary but for all the compartments on a Harley. If that is not something you feel like doing, at least put the correct primary oil in your primary (as far as your service manual is concerned) which is Formula Plus. (also made by Harley). And when you say your primary is "full of oil",what exactly do you mean? Filled to spec or completely full? Anyways,Of course this is just a suggestion.

[coolhawg6622]

You should be using a 20w-50 oil. The 10-40 is too thin. Thats why it didn't leak when it was cold,once it warms up it thins out and finds a way to get out. I personally recommend Amsoil 20w-50,not only for the primary but for all the compartments on a Harley. If that is not something you feel like doing, at least put the correct primary oil in your primary (as far as your service manual is concerned) which is Formula Plus. (also made by Harley). And when you say your primary is "full of oil",what exactly do you mean? Filled to spec or completely full? Anyways,Of course this is just a suggestion.

First Harley doesnt make a drop of oil....... Seems you believe alot that you read..........10/40 in a primary is fine I run it and have in all the bikes I have had........ Matter of fact I believe there is Rotella 15/40 in there now....... I better get home and drain it quick as I am sure Deisel oil will wreck it for sure......

I know a few guys that are running ATF in the primary.......

[Padog]

Good info!
I just recently had a totally opposite situation with Mobil 1 oil - my daughter has a twin turbo Audi and it calls for 0W-40 (yes not a typo its 0) The local autoparts only stocked that weight oil in mobil1 synthetic which I thought was fine so thats what I have been puttting in her car. last oil change I pulled one of the intercooler tubes and found oil had collected in the bottom of both tubes at their lowest point I thought for sure her turbos were headed south!

I jumped on the audi forum and asked a few questions and to my surprise many had experienced the same problem they said to switch back to a dino oil or use Mobil1 5w-40 and it would go away. I switched to the 5w-40 and havent had any oil in the tubes since. Not knocking Mobil1 at all it just seems the 0W synthetic is so thin it wicks through the turbo seals and ends up in the intercooler piping???

[Horse]

You should be using a 20w-50 oil. The 10-40 is too thin. Thats why it didn't leak when it was cold,once it warms up it thins out and finds a way to get out. I personally recommend Amsoil 20w-50,not only for the primary but for all the compartments on a Harley. If that is not something you feel like doing, at least put the correct primary oil in your primary (as far as your service manual is concerned) which is Formula Plus. (also made by Harley). And when you say your primary is "full of oil",what exactly do you mean? Filled to spec or completely full? Anyways,Of course this is just a suggestion.

First Harley doesnt make a drop of oil....... Seems you believe alot that you read..........10/40 in a primary is fine I run it and have in all the bikes I have had........ Matter of fact I believe there is Rotella 15/40 in there now....... I better get home and drain it quick as I am sure Deisel oil will wreck it for sure......

I know a few guys that are running ATF in the primary.......

I use Amsoil Super Shift (ATF) in the primary, Amsoil Sever Gear 75w-140 in the trans with Amsoil 20w-50 in the engine. Great combo in my 93FLHTP (71K).

[Heretic]

I know a few guys that are running ATF in the primary.......

That brought back memories.....in the old brit bikes, I used to plug off the oil seep for the primary (then ran bypass oil into the primary). I would then fill the primary with a mixture of STP and ATF...

well that is what I did, until I discovered primary belts