from the horse's mouth

From the package of new Barnett clutch plates...

"ATF? Type F will give you a harsher, more positive clutch engagement. GM (DEXRON) will give you a smoother, more linear engagement.

"Never use automotive oils."

I used GM ATF yesterday, cannot make an appraisal of it yet. I have always used Type F because it has always been recommended but if Barnett says Dexron is good with their plates then I am willing to try it.

I don’t understand why they would say not to use automotive type oil. Unless they are using special friction material for Norton and any other company that has a separated primary. I am willing to bet the vast majority of motorcycles share the engine oil with the clutch pack. I’m curious to know what would be their recommendation in that case. My thinking is any oil that is MA or MA2 approved should be fine, and that could be the difference between “automotive” type oil and “motorcycle” type oil. That being said, if I had a ‘74 or earlier I would be using ATF anyway.
I ran Castro’s GTX in my Gold Wing for years with no problem, my buddy is in the process of replacing the clutch plates in his Shadow with only 20k on it. Honda mechanic blamed it on the fact he didn’t use Honda oil.
More oil “voodoo” I guess.

the type f was formulated for a bronze clutch plate that was in use in the 50's and early 70's cast iron transmissions and GM used an asbestos based lining so type A was the recommended fluid. as things changed to an organic based friction than dexron became the fluid to use. now there are numerous ones for different OE's for shift quality; the type F has been an old hot roders trick to get a firmer shift and some like have gone to making there own fluid like the B&M trick shift. i would stay with the dexron on a barnett plate if you are running it in a wet primary.

seattle##gs said:

From the package of new Barnett clutch plates...

"ATF? Type F will give you a harsher, more positive clutch engagement. GM (DEXRON) will give you a smoother, more linear engagement.

Click to expand...

Just put in a set of Barnett plates and used the type F because I had some on the shelf. I wouldn't say it was harsh.

73 850 with Barnett clutch soaking in Harley primary chain case oil. It's worked well for 15,000 miles. I'd always used transmission fluid both Ford and GM, but I didn't have any around the garage when I put in the new clutch so HD got the call.

Further on..." We recommend using only motorcycle specific oils that meet the JASO-MA, JASO-MA1 OR JASO-MA2 (NO FRICTION MODIFIERS) specifications. These oils meet the special needs of motorcycle clutches and transmissions."

I always use ATF except for MK3 but now I know there should be no problems using the GM ATF.

Deets55 said:

I don’t understand why they would say not to use automotive type oil.

Click to expand...

Modern auto oils have friction modifiers added to get better mileage etc, the clutch is outside the engine on manual gearboxes so oil free. so they are formulated with no intention of allowing for a wet clutch. So stick with ATF which is designed for wet clutches inside an auto gearbox or Motorcycle oil which also does not have the friction modifiers due to the need to cope with a wet clutch.

kommando said:

Modern auto oils have friction modifiers added to get better mileage etc, the clutch is outside the engine on manual gearboxes so oil free. so they are formulated with no intention of allowing for a wet clutch. So stick with ATF which is designed for wet clutches inside an auto gearbox or Motorcycle oil which also does not have the friction modifiers due to the need to cope with a wet clutch.

Click to expand...

Kommando,
I follow what you are saying, but here is where it gets confusing to me. I use Rotella T-6 in my Gold Wing and my Norton primary. It is not marketed as a motorcycle oil but meets the MA and MA2 standards. I don’t have Barnett plates in my Commando so I can’t speak from experience on how compatible they are.
I think seattle##gs may have clarified this point for me.
Pete

I have a 78 Bonneville that shares engine and primary oil. I use dino Valvoline 4 stroke 20w/50 oil in it which is Jaso MA2 standards. The discs are the orange kevlar type from Map Cycle. It works as well as any of the clutches in my other bikes.