Primary Chaincase Oil

WEM

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I’ve noticed several Forum members have recommended ATF for the primary chaincase lubricant. The Workshop Manual specs 20W/50 oil. What are the pros of ATF vs the OEM’s recommended 20W/50?
 

elefantrider

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1. Clutch is supposed to slip less with type F ATF.
2. If you have a leaky bike, you can better see if the leak is coming from the primary or the engine.
 

Tornado

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AFAIK, the main reason for a lubricant in primary is to keep chain happy. We all run the drive chain in open air exposed to grit and crime and give it a wee clean and lube every so often. The primary lives in a much cleaner environment and gets nice splash of clean lube at all times. Nice Digs!
So the choice of lubricant should make very litte difference to performance or longevity of chain/sprockets. And if levels are kept to spec than clutch contamination should be minimal.
I use atf-f
 
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Just one thing to add and that is at times I've been guilty of daydreaming and adding too much, .... but since the switch to ATF-F don't suffer from slip on the clutch near as much as with heavier oil. Of course primary leaks are quickly found out as mentioned reducing head scratching somewhat on puddle origins.
 

texasSlick

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Agree w/ jbruney, and elefantrider, ATF type F is said to have 35% more coefficient of friction than motor oil. However, be aware that ATF is tough on sealers!

I had catastrophic failure of RTV sealer on my Atlas outer chaincase after about 2 years of use. I found a puddle of ATF on the floor one day, and no hint of it the day before.

Best sealer for use with ATF is Permatex #81180.

Slick

 

Tornado

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Just one thing to add and that is at times I've been guilty of daydreaming and adding too much, .... but since the switch to ATF-F don't suffer from slip on the clutch near as much as with heavier oil. Of course primary leaks are quickly found out as mentioned reducing head scratching somewhat on puddle origins.
Isn't ATF supposed to be a non-Newtonian fluid, that thickens when undergoing shear forces? Hence why it works in automatic transmissions.
 
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In the 70s motor oil didn't have the additives that stop clutches slipping and sticking and the motor oil was to heavy for the clutch, when I brought my 74 850 new the clutch worked great no slipping at all then after a few months things started to go wrong with the clutch, in them days GTX motor oil was the recommended oil to run in our Nortons and after the first oil change the GTX oil was so black on the case and no good on the clutch plates as well made the Norton run hot in our hot summers, so I started to run straight 50 Pennzoil and the expermenting with light oils in the Primary to stop the clutch slip from the oil, I ran hyd. oils 2 stroke oil then finaly ATF -F brand which stopped all slipping of my clutch and sticking plates, the F brand ATF is designed for early Ford transmissions that had clutch plates.
I have been running the ATF-F for over 35 years now I only do min maintenance on my clutch once a year a full pull down and clean of plates but most of the time they are still all good but its just part of my maintenance, I only run between 5 to 7 fl.oz in the primary and no more, a lot of folks think more oil is better, but no and think because the bottom of the chain needs to be covered in oil in the bottom of the primary but no the chain lube relies on the oil splash from the oil, over filling the primary will cause other problems, I messure all fluids that I run in my Norton from primary to GB oil to how much oil in my oil tank and because I messure my GB oil I have never had GB oil find its way into my Primary case or clutch.
I run wet clutches in my modern Triumphs, motorcycle motor oils designed for wet clutches so not sure it the modern motor oils of today are any good with the Norton clutch but I been running the ATF-F oil for so long and happy with how my Norton has never had slipping clutch since using it all those years ago, so I stick by it and use what works for me.

Ashley
 

DogT

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I also never had a clutch problem with the recommended oil. Another anecdotal data point.
 
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