Yep, I used to use Golden Spectro semi synthetic in my tranny (84 FXRS). Never had any problems, shifted smoooooth as silk.
You're wrong.Unome said:Correct me if I'm wrong but isn't the primary similar to the differential in rear wheel drive cars?
paphigliano said:We have found for stock bikes any oil in the primary will work some better than others, but if you are a big bore boy or a stroker nut ;that the synthetic gear oils,,,,,75/90 really make the clutch hook up. I have built 110hsp motors and used the stock clutch spring as long as you use the 75/90 in the primary,,,,,,if you use 10/40 or 20/50 in the primary on these style of motors you will need to upgrade the clutch spring,,,,,,its the way it works around here for us anyways.