1975 E/S MK3 Primary Oil ATF or Engine Oil

After reading many blogs on the subject and after replacing my crank sprocket and sprag plus the needle roller bearing and hardened sleeve on the starter gear I decided to use ATF oil in the primary. Is their any recommendations of the best make to use that is available here in the USA. I have noted a little clutch noise with the ATF versus the engine oil. It would be interesting to know how many miles owners have covered using their electric starts with ATF versus the recommended back in 1975 engine oil
Thanks

Your primary chain tensioner will not like the ATF and lose its prime so stick with the recommended 20W/50 oil.

kommando said:

Your primary chain tensioner will not like the ATF and lose its prime so stick with the recommended 20W/50 oil.

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I always run ATF and haven't had that problem [unless it sets for several months without being run]. Jim

I used to run with ATF, but went back to 20/50w and all seems well. No clutch slip and I can't remember having problems with the tensioner with either type of oil......but then it's rare for my bike to sit for a long time without moving uless it's in bits

Best of both worlds: use 20W50 engine oil (for the tensioner) in combination with a set of Barnett clutch plates (no slip) :wink:

Can't say which is better choice. I use 20-50 W. Today's modern oils are way superior to 40 years back and everything works as it should.

I've used ATF in my MK3s for a number of years with no problems. When I got my first MK3 back in the late '70s, I used 20-50, and I don't recall having any real problems with it either.

Ken

When I bought my Mark III, I immediately changed all fluids. I put ATF in the primary and experienced chain slap when
the engine was cold. After warming up it went away. Then I drained the ATF and put in 20-50. Now no chain slap ever.
I'm running original bronze clutch plates and never had them slip.

I put 20W50 in my primary and don't have a slippage problem, quite the opposite. I pulled the clutch apart on the weekend and degreased all the plates and it looks perfect. One question, I fitted the Barnett clutch plates but the driving plates are steel and don't have the offset groove, could that be why it clags up ?

Mk3 running Type F atf here and no problems. When I first got the bike years ago the clutch would drag, neutral was hard to find and it would pop out of first gear sometimes. A fellow Norton owner suggested switching from motor oil to type F atf and that cured those problems
I have since added a DynoDave pushrod seal, Barnett Kevlar plates, and a Venhills cable. The clutch on the Commando is a treat to use.
I seem to recall reading somewhere that type F gives more grip than the other ATF types do.

Glen

I run 20w50 in my engine and primary, being sure that they are JASO MA rated oils. It states right on the bottle that they are formulated for wet clutches.
No slippage problems at all on my MK3. I use Valvoline motorcycle specific oil, MA. There are other manufacturers, just look for MA.
Jaydee

The last time I had the primary apart I didn't have any 20-50 but gallons of Shell Rotella T 15W-40 diesel oil so that's what I used. Since then I've noticed that I no longer have the drag that makes neutral a bit of a problem to find. The clutch has never slipped on either 20-50 or 15-40. I only add the required amount and do not fill it to the witness hole. It's just an observation.

I think it was straight 20 grade for the primary case rather than 20/50 wasn't it?

daveparry said:

I think it was straight 20 grade for the primary case rather than 20/50 wasn't it?

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Yep.

About like ATF -which still contains good anti-wear ingredients that are now not in motor oil due to environmental concerns. ATF is a the better lubricant for a sprag clutch. Jim

Jim, a little question for you if you wouldn't mind. I've used ATF in primary chaincases for years without problems but i've recently re-built a 1969 BSA A65. I was advised by a well known BSA specialist not to use ATF in that primary so I used straight 20 grade but i'm having awful trouble with a dragging clutch. I've cleaned the plates again and checked them for straightness, adjusted the clutch rod and cable etc. but it's still not nice! I'm now thinking of cleaning the case out yet again and trying my old faithful ATF, worth a try do you reckon? It uses that Triumph type 3 ball lift arrangement for the clutch release, something i've never been a fan of!
regards,
Dave.

daveparry said:

I think it was straight 20 grade for the primary case rather than 20/50 wasn't it?

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The manual states 20/50 w grades for the 1975 Mark 3

OK Thackero, my mistake, i've never had a Mk3.

daveparry said:

Jim, a little question for you if you wouldn't mind. I've used ATF in primary chaincases for years without problems but i've recently re-built a 1969 BSA A65. I was advised by a well known BSA specialist not to use ATF in that primary so I used straight 20 grade but i'm having awful trouble with a dragging clutch. I've cleaned the plates again and checked them for straightness, adjusted the clutch rod and cable etc. but it's still not nice! I'm now thinking of cleaning the case out yet again and trying my old faithful ATF, worth a try do you reckon? It uses that Triumph type 3 ball lift arrangement for the clutch release, something i've never been a fan of!
regards,
Dave.

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Well i am certainly not a BSA authority but I see no reason why ATF in the primary would not work.

I don't know if that is the answer to your sticking clutch plates but ATF contains all the necessary ingredients to lube it properly.

Thanks Jim, i'm going to try it.

I was told by mr Phil Heath who helped with the development of the original Norton pressed steel oil bath CHAIN case that the correct grade of oil to use was a thin straight SAE10 or 20 oil IF you actually want to lubricate the great many plain bearings that comprise your primary drive chain....especially at the rediculously high linear chain speeds we use. Lubrication being required to keep efficiency above 90% and to keep the chain from glowing red hot as anyone who ever used a pinky to check primary chain tension on a G50 after a couple of laps of the TT course can tell..i.e. ME and I was fairly used to the smell and pain of burning flesh having in my youth spent 6 months of my 5 year apprenticeship working in a blacksmiths/welding shop......I NEVER used my pinky to that job again. I think it was called a learning curve.
Of course anyone who has ever read a chain manufacturers design manual knows that correct lubrication at the chain speeds we employ is sump and pump. Mr Heath said to me of the oil mist system as employed by Norton ......'It does little for chain life'. I laughed.
The MINIMUM life given for a Reynold chain is 15,000 hours use or at an average speed of 40mph 600,000 miles and this I would suggest is a good indication of how incorrectly we use and lubricate our primary chains.
AND dont forget that the Commando clutch was designed to be employed DRY so the next to last thing you need on the friction interfaces is oil and the last thing you need is friction inhibitors within an oil!. Of course if you dont put much torque through your clutch the clutch slip due to oil on the friction interfaceswill not be a problem for you!!
In my young days we were recommended to employ Castrolite in our primary chain cases, a thin SAE 10-30 oil (or was it 10-40??) which has not been available in the UK for a while(so someone at 'Castrol' told me a few years back). Castrolite is I note recommended in my BSA A65 workshop manual for primary chain case use....the chain case being developed in the first place to give the chain a better form of lubrication than given to it by mud, water, stones and human flesh / bones which photos clearly show were the lubricants used on my late Fathers Nortons in the 1920s........along with a drip fed oil supply which is ok for a chain moving slightly faster than that of a slow moving snail....like the ones that traveled across the floor of the marshals huts up on the mountain section of the TT course in the 60s and 70s...especially in the clouds wind horizontal rain and sleet before dawn breaks and early morning practice is eventually cancelled due to the weather!!