What type of oil goes in the Primary Case of a '86 Harley Sportster?

20w-50,... just like the motor. Do make sure it is NOT automotive oil, especially "energy conserving" oil. (it has additives that will make the clutch slip) You must use an oil marked motorcycle oil, as it designed for motorcycles, with shear tolerance capabilities, heat transfer additives, and viscosity stabilizers, among other things.....

(edit) As usual,... Do not lend one ounce of credence to the poster whose avatar rhymes with fart. He does not even ride a motorcycle, and has absolutely NO expertise in any discipline concerning motorcycles. He jumps at the chance to confound, contravene and compound any issue relating to Harley Davidson, the riders and their choice of equipment. He holds No credibility in this community or any other....

There you go Bart - I just reported you for giving misleading information of which could be harm full.If you don't know $hit shut up!There are no warranty issues with the oil if it is the correct spec. & quantity.My dealer likes me regardless of spending $10 or $10,000 or just call in to look around 'cause I am not a total jerk like you.

You put Sportrans in it, if you go to a place other than the dealer that has HD accessories they may call it something else but they should know what you need and have it.

Harley Davidson BRAND, Screaming Eagle Synthetic

It MUST be Harley Davidson Brand Oil that's specially formulated for Harley Davidson

any other brand of oil is TOTALLY UNACCEPTABLE

(the local Harley Dealer will like you better if you buy oil from him)