Harley Oil 58, 75, 105

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Re: Harley Oil 58, 75, 105

Postby 57XL1002 » Thu May 30, 2019 8:04 pm

Here is a worthwhile primer on motorcycle oil for those who assume that everything is better with Blubonnet On It. http://www.motorcycleanchor.com/motorcy ... tml#WYRNTK It also relates to Dave's curiosity of why HD used the peculiar Oil Grading (SAE)(API CLASS RATINGS)( JASO-MA specification) system they did. Oils are rated at both flow and lubricity (?) at certain oil/engine temperatures. The low end of the spectrum is 40*c (about 100*F) and the upper end 100*c (about 210*F). 58*c = 136*F, 75*c = 167*F, 105*c = 221*F. This basically is how multi viscosity oil is graded, at the low 40*c and high 100*c levels. Also why we have oil coolers. I know we wern't into metrics then, but science was. Most of this is just my guesswork, without the original engineers to explain their reason, there is nothing else left to do. I'm 72 and been professionally involved in racing for over 50 years, and the best advise I always gave my customers is, never drop the hammer till you see 180* on the temp guage uno peso...
Last edited by 57XL1002 on Sun Sep 15, 2019 5:14 pm, edited 1 time in total.
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Re: Harley Oil 58, 75, 105

Postby hennesse » Thu May 30, 2019 9:11 pm

And here's another example of Harley 75 = SAE 40.Look here AMF, perhaps later 1970's ???
Harley 75 = SAE 40 (at least that year)
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Re: Harley Oil 58, 75, 105

Postby Bubbalowe » Fri May 31, 2019 9:21 am


Viscosity comparison charts show overlaps between Saybolt and API. MOCO used SUS in olden days.
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