Quote:

Originally Posted by Revnharley

AMSOIL Synthetic 20W-50 Motorcycle Oil ...

wtf? Do you have a bot doing these posts?!? This post is identical to the one you spammed into the What Primary Oil is your Choice forum.

spam alert!

 

50W engine oil has the same viscosity as 90W gear oil. Engine and gear oil just have different grading systems. 60W engine oil would be the same as 140W gear oil.

 

If you check Amsoils site their MCV 20W50 is pretty much the same viscosity as their 75W110 gear lub and the 75W140 is pretty much a 60 wt oil. Their 75W90 is pretty much a 15W40 oil or a 40 wt., which I believe is too thin for our transmissions in the twin cams. The Amsoil site calls for the 20W50 first, second their 75w110 and third their 75W140. I had a 1992 FXR and ran the Amsoil 75W90 in it and their 10W40 in the prim., as they called for back when. i have the 2007 FXDL which has the six speed and if one has a twin cam with a 5 speed maybe the 75W90 might be ok but with the TC making more power I would not us a 75W90 in it. I now have the 75W110 in my trans ans will most likely put the MCV 20W50 back in as it worked great and that is what Amsoil calls for first on their list to use. It only has a GL rating of one where else the 75W110 and1 40 have a rating of GL 5. I would think if we really needed a GL 5 rating then Amsoil would have that first on their spec sheet to use and not their MCV. The GL5 is not good for yellow metals but do we have any in our Harley trans be it a 4,5 or 6 speed??? My 2 or 1 cent. Ride safe eh.

 

Amsoil 20/50 in engine & primary
Amsoil 75/140 in trans

 

Harley used to use 75w which was 40w and 105w which was 60w. I have a '86 fxrd with 108,000 on it ,I use 10w40 amsoil in primairy as HD recommended 10w40 when their primairy oil ran out ,but I only put in 1 qt.Tried primairy+ ,but that clunked into gear loudly when cold ,75+ degrees out.Trans uses amsoil 75w140 as it gets a little noisy when hot,works same as 75w90&have used redline also with good results. Motor I use 20w50 amsoil.I also put 2 oz. Ford friction modifier in primairy.
As clutch was noisy I replaced clutch discs with new drag specialty discs, I can pull clutch count to 2 and it goes into gear with no clunk or noise.Still rattle in clutch think basket is next step.

 

You're confusing the old HD designations with actual viscosity. HD's designations were Special Light 58, Medium Heavy 75, and Regular Heavy 105. These were straight viscosity oils and essentially corresponded to 40, 50, and 60 weight, respectively.

 

Amsoil 75-110 shifts great.

 

What about Redline Tranny lube for v-twins. That stuff has the Heavy Shockproof in it and it's rated as a 75w250. Isn't that a bit to thick for the needle bearings in our trannys? Especially on a cold day.

 

I'll let those who know more give a full answer, I just wanted to point out that the 75W part of the rating is the 'cold flow' (W=Winter) part of the rating.

fwiw.

 

On the topic of oil changes, how often should the oil tank on a '89 FXRS be removed to flush out any sludge? I'm not sure if this one has ever been done. Cooter