Gearbox & Primary Lube Quantities?

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Dec 15, 2006
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New listee here, first post. This is a cross-post from the INOA list where I recieved little help.

Been a while since I've worked on a Norton so please excuse my
ignorance. The bike in question is a 1975 E-Start Commando. I seem to
remember that its recommended to measure out the quantities
of oils when refilling the gearbox & primary chain case vice relying
on the "full" plugs. Could anyone please refresh my memory on those

Also, I recall that ATF was recommended as a good substitute
for the primary lube. Would that also apply to an E-start Commando
given that it has a hydraulic primary chain damper? Or is SAE 20-50 a
better lube for this application?

Thanks for the help,

Joe in St Louis
I always use the gearbox and primary level plugs (850 MkIII) I don't think there is any benefit running the MkIII with minimal primary oil because the splash fed tensioner needs a reasonable supply to operate.

I used to use ATF in the primary because that is what gets recommended these days and also because that was what was in there when I bought the bike.
But I did hear opinions that ATF was too thin for the hydraulic tensioner, so I tried multigrade engine oil and the transmission certainly seemed smoother at low engine speeds (less snatch) and also the primary drive was noticeably quieter. The engine oil did not appear to affect the clutch operation at all.
I've always measured 200cc into the primary chaincase which is slightly less than the level plug indicates. One useful point in doing this is that if you check the level in the future and it starts trickling out, you will know that it has come from somewhere else.

I always make a point of filling through the timing inspection cover because it occurs to me that filling via the clutch adjusting cover would pour the oil directly into the clutch which is not really where we want it.

As L.A.B., I tried ATF at one time because it was the thing to do but found that it drained too quickly out of the tensioner. I'm probably going to get shot down in flames for this but I tend to use left-overs of old fork oil (around 20 weight) If it works in a hydraulic damper then it should work in a hydraulic tensioner was my reasoning and I have not noted any ill effects with clutch or chain.

On the gearbox side, I fill to the level plug which can be seen through the inspection cover from inside. No need to trickle EP down the inner cover to join the stream running down the mainstand spring :)
I too have an 850 MKIII. I use 20w-50 in the engine and primary and 90wt gear oil in the gearbox. I use the oil-level plugs/indicators for determining the correct oil volume. I use ATF only in the front forks.
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