I just run Pennzoil 10W40 in my primary, with no clutch slippage.

 

Mobil 1 20/50

 

OK, this has me a little worried. I'd heard from a buddy of mine that ATF was good in the primary, said he'd been using it for a long time with no problems, and he uses Type F. So, this morning I went and bought some and changed my primary fluid with it, haven't ridden with it yet since it's raining, and now I'm wondering if I shouldn't go get some 20w-50 and change it out for that. Do you guys think it'll be alright for 2500 miles with the Type F? I think it should be, but any input would be appreciated. Also, what makes Type F bad, if it is?

 

I have used B&M Trans fluid and Amsoil super shift For the last 35,000 miles and see no difference or harm in any way . Shifts fine .

 

The ATF should be fine. Ride for a bunch of miles and see how you like it. Many report that the type F gives a bit quicker clutch engagement (grab) then does either Dexron or motor oil.

 

Many, many people use ATF with no problems.

 

A friend has been using ATF Type F in his 2000 EGC now for 60k miles with no problems. I've heard tales that ATF eats at the stator adhesive, coating, or whatever--but if it even happens I've never actually seen or heard of a case of this causing a problem.

I use Castrol GTX 20w50 and see no issues at 37k. To change the mainshaft bearing in the tranny I had to disassemble the primary at 32k miles, and nothing looked worn. The tensioner, chain, main bearing, and clutch disks were in fine shape and were re-used. Clutch action is excellent and I have no slippage (even with the SE255 cam upgrade) or drag. I don't think it really matters much what you use in the primary, but I wouldn't use a high-tech synthetic or any other oil rich in friction modifiers, as these are not good for clutch operation. Besides, the primary isn't a high-tech environment and any oil over $4 is overkill, IMO.

 

I tried AFT for a week and didn't like how my clutch felt, out it went tonight and back to 10w40 dino oil.

 

I've seen several bikes run regular 10W40 motor oil in there for uncountable miles with no wear problems. I decided that since it gets changed only twice in a lifetime or thereabouts, that I'd run the Amsoil. The dino oil that was in it had some crap in the bottom, but that could have been break-in junk from the clutch plates.
Clutch action is perfect, especially in cone riding where I need it slipping constantly. Stays cool too. I expect that ATF is thinner and could run a little better on fuel mileage but the cost of primary oil is negligible when you're spending $50 for each engine oil change plus the filter!

 

What would happen if a crank seal went, and it started to draw atf into the crankcase hmmm?.,,