I think no. Heavy viscosity oils were used in older bikes sorta like "spacers", for the large variances in manufacturing tolerances. As good as synthetics are, I don't think they can make up for that. I could well be wrong, and don't mind knowing if I am.
No No No you have roller bearings use the 60w. Make sure it cycle oil or at least the Valvoline racing. It contains zinc in it, those old motors need it for lubrication.
Peep,
When your older bike calls for 60w straight weight oil... A reason for it.
I have not checked a lot of oils today but I know Redline makes the heavy "single weights" yet and I would definitely stick with the Viscosity they recommend. That being the 60w
The 60w is needed to take up the slop that using a 20w50 won't do...
The oil pump is designed for a straight HEAVY weight oil and the clearances in the engine are designed for the same.
A big difference in the SINGLE weighted oils than the "multi weight" oils of today...
mine? I would use the single weight 60w, and a synthetic for the added wear protection and heat...
Use the single weight 60 if "normal temperatures"...but if you are running in the 40's or 30's, you may want to consider 50W just to make easier cold weather starting during the winter months. The older engines had more bearings that were roller type and do not need so much oil pressure to "pressurise thin film of oil around thrust bearings and oil gallery grooves" to keep from metal to metal contact...so much more in use today. Also the high detergent levels make thinner oil films and more particles in suspension today possible, more so than in the past.
When it really gets hot I ran a Catrol 70 wt. But mostly 60 wt. during the normal summer heat. I ran this in a 48 pan I had 25 yrs ago. Sure wish I still had it. Everyone is right about the bearings and stuff.
they didnt run 20-50 until 1984 so st8 60 wt is the right stuff ! I run Amsoil 60 racing oil in my 59 Pan....
In colder weather I run 50wt. and 70wt if its going to be 90f plus everyday