Sporster Primary/gear box oil?
 

I have a 2009 sporster. I was wondering if anyone has experince with a good gear oil for wear protection and low friction. The people on the xl forums are suggesting mobil 1 75w90 gear oil.

I know this is an old thread, but I've got some experience to relate to you about gear oil.

I'd been using Lucas 75W-90 Synthetic since the bike was new, but each time I drained the gear oil, I noticed it was "glittery"... meaning I was getting gear wear.

I switched to Royal Purple MaxGear With Synerlec 75W-140, and the "glitter" immediately went away. Yeah, it's a thicker gear oil than the manufacturer recommends, but it works.

But if you *really* want low friction and low wear, do what I'm having done... get the gears micro-polished and coated with tungsten sulfide. I'm using MicroBlue to get that done.

Tungsten sulfide has the lowest coefficient of friction of any metal treatment out there, it'll make the surfaces of the gear teeth so slick they can't wear. Combine that with the micro-polishing, and your gears will be low-friction and last forever.

Taking it to the extreme, as I'm doing, put hybrid ceramic bearings in the rear gearset. I'm using MicroBlue bearings. They've got silicon nitride Cerbec bearing balls, the races are micro-polished and both the balls and races are coated with tungsten sulfide.