Mk3 Primary case oil

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hillbone

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What oil and type do you guys recommend for the primary case on a Mk 3?
 
Type F ATF
Reason being , all we need to do here is keep the triplex chian lubed. ATF has tremendous ability to do this yet has little effect on dry clutch plates.
 
F type is good advice but not on a mark three. Dyno Dave pointed this out long ago on this site when I said the same thing. A mark three is a very different bike than the 74 and back bikes. Hundreds of engineering changes on this bike it needs its own forum really. They are that different. Oh well another thread another vote ……
 
I use 20W-50 in my MarkIII.

Rumor has it that because of the Automatic Chain Tensioner in the MarkIII, oil is the way to go.

ATF seems to be the way to go for anything pre-MarkIII.
 
In my MKIII I use what ever is in the motor. Usually a 20W-50 of some sort.
 
Multi-vis 20/40 or 20/50 (I like castrol)

The e-start stuff and auto chain tensioner won't like ATF.
 
pvisseriii said:
all we need to do here is keep the triplex chian lubed.
Click to expand...

Not so for a MkIII, because the operation of the MkIII hydraulic chain tensioner can be affected by the oil type.

Personally, I prefer to use what the factory recommended = 20w-50 engine oil.
 
I did try ATF in the Mk 111 years ago and discovered for myself that it drains out of the chain tensioner overnight. The tensioner does not of course have any seals so relies on close tolerances and thick oil to keep anything in the reservoir.

Close tolerances are sometimes a little hard to find on Commandos so that leaves us with the thick oil option ! :)
 
The book recommends engine oil, so straight 50 or 20W50. I think what has been said about the hydraulic chain tensioner is correct. Plus, ATF, with seal-swelling additives, may have an adverse effect on fiber clutch plates.
 
Danno said:
The book recommends engine oil, so straight 50 or 20W50.
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The 850 MkIII Manual and Riders Hand book recommends 20w-50 engine oil for the "Primary Chaincase". However this may not be the same oil you use in the actual engine, as the preferred recommendation for "Engine Oil" was for HD40 or HD50 monograde or 20w-50 multigrade.
 
I'm using Rok 10-40 in my Mk.1 850 & have not a clutch slip problem for a year. 1st time. It is just a thought if you suffer from gooey clutches.
 
thanks for the feedback. looks like engine oil is the go. the reason for my enquiry is more about the chaintensioners and keeping them working properly.thanks
 
Ever since I lightened the rockers, eliminated the base gasket, matched the carbs to the manifolds and the manifolds to the heads, added a 2-into-1 pipe and jetted up, the all metal MkIII clutch has slipped when it hits 5500 rpm. I bought a Barnett clutch plate set and as soon as I find my clutch tool, the slip will be gone.
 
L.A.B. said:
pvisseriii said:
all we need to do here is keep the triplex chian lubed.
Click to expand...

Not so for a MkIII, because the operation of the MkIII hydraulic chain tensioner can be affected by the oil type.

Personally, I prefer to use what the factory recommended = 20w-50 engine oil.
Click to expand...

My bad!
 
Note that Automatic Trannies have clutches - usually two clutch packs that look pretty much the same as a Norton Clutch pack. So from a clutch point of view, I'd think that ATF is a better choice. And since automatic trannies also have gears and need lubrication for rotating/turning parts, it's clear that ATF lubricates adequately in that sort of application. The impact of the chain rollers on teeth and gears hitting gears seems like essentially the same thing...
 
MexicoMike said:
Note that Automatic Trannies have clutches - usually two clutch packs that look pretty much the same as a Norton Clutch pack. So from a clutch point of view, I'd think that ATF is a better choice. And since automatic trannies also have gears and need lubrication for rotating/turning parts, it's clear that ATF lubricates adequately in that sort of application. The impact of the chain rollers on teeth and gears hitting gears seems like essentially the same thing...
Click to expand...

Except you didn't read the part about the MkIII chain adjuster.
 
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