Does anybody run automatic transmisson fluid in primary? If you do what kind? Seems to me it would work good. on the clutch pack. They are probly just like clutch in auto tranny.Any comments?
I've heard of people running ford type "F" in the primary but wouldn't do it in my bike. Run what was made for the bike/primary for best results. Almost anything would work in the primary but if you have to buy it, why not buy what belongs in there instead of substituting something else.
At the 1000 service i put amsoil 20W50 in there.I dont know but the bike seem to lose a little of its zip. At 2500 i put HD primary back in. The clutch seem to hook up better.
Now there ya go, you answered your own question Actually a light oil in the 10/40 would work well in there and that's about what the older HD primary fluid was. The key here is not to use a synthetic oil or an energy saving oil like 5/30 or so in the primary mainly because of the additive packages in them. The heavier the oil, the more it will be prone to clutch plate dragging when the clutch lever is pulled in. The heavy weights actually cause the plates to spin a bit from the "drive" that the heavier oil is causing which will cause hard/noisy shifting and problems finding neutral. Synthetic oils are designed with additive packages to reduce friction and clutches NEED friction to operate properly. I think you can see where this is going. Some use synthetics in the clutch/primary area and report no problems at all but as the clutch wears, the problem begins then when the friction is reduced and the clutch then slips.
Sorry, I'm a little late to the party, as usual. I actually used an ATF fluid in the primary, on reccomendation from a friend. I really didn't notice any difference in operation, but never felt comfortable having it in there. It bothered me so much I took it out after a couple thousand miles. I wasn't really worried about the clutch, but more concerned with the primary chain and sprockets. On the other hand, I do use a synthetic in the primary, Mobil 1 Racing 4T 10W-40. This oil is made for wet clutch operation, and it seems to perform well. I think it will also provide a little better protection for the chain and sprockets. Maybe I'm just a little paranoid having had a primary chain break on me a few years ago. Ok, quite a few years ago.
I feel the same as you about running ATF in the primary. The friction modifiers in a synthetic oil is what causes the problems with slippage in the clutch pack. Other than that I see no problems with a 10/30 or 10/40 oil in the primary as long as it doesn't contain friction modifiers.