Primary oil level

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Oct 27, 2007
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On my 71 Commando I noticed when filling my primary that when filled to the correct level and capacity that the chain doesn't even come close to the oil. I put in 200cc/7 oz and even when I overfilled it 4 oz that it still didn't come up to the chain. Was about 1/2" above. I measured the oil and also had the fill plug out. I tried it on both the center stand and side stand with the same results. Anyone have any ideas. All I can think of is that the motion of the bike keeps the chain oiled and/or the moving chain creates enough airflow to keep the chain lubed.
 
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Remember the chain goes lower than you can see looking in through the inspection caps, it just needs to dip into the oil, no need for it to be covered as it drags it round and flings it all over.
 
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Feb 8, 2007
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Hi, another thing, take off one of the inspection covers while the bike is at idle and see just how much the oil is sloshing around in there - amazing.
 
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I forgot to mention that I kicked it over several times and the chain remained dry. I'll take the top plug out when I start it to see.....
 

concours

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I am concerned about this too... it flies in the face of every industrial and automotive drive I've ever worked on, violating the rule of at the very least, the lowest turning parts must be in the lube to sling it. I understand about the catenary effect of chain at speed, don't think it moves down a an inch. But the level plug is WAY below the chain, even at the rear where the clutch makes it the lowest. The outer primary cover has a boss cast in for the level plug drilling which is 3/4" higher than the drilling. Evolution? Looking for thoughts, experiences, views. Please, let's leave the "it ain't a wet clutch" debate OUT of this thread, that's another kettle of fish altogether. I'm talking about enough lube to make the chain and sprockets live.
 
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Real Nortoneer's know that the 750 models all had factory fluid levels set too hi if going by the manual or the dip stick or the level plugs, except the forks of course. The only reason chains need lube at all is 2 reasons, one to flush their wear particles out plus keep grit on the outside *and* to remove heat, *IF* heat is even a factor in its application, but not really to lube in the lowering of friction sense. Proper primary lube w/o electric starter hydraulic tensioner, it just touching the bottom links when cold and sagged. I ain't debating just reporting the facts and also that thinner oil like ATF is way better than engine oil in primary. Racers found out the hard way anything over 20 grade can seize their chain. The alternative to ignoring these facts is a messy bike and grimed clutch plate trouble to service and remaining un-informed on chain operation physics to keep repeated the mess and hassle. Third advantage of ATF is easier to tell source of leaks.
 
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Put it on the side stand and add fluid to the fill hole till it drips out the OIL LEVEL PLUG.
 
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Put it on the side stand and add fluid to the fill hole till it drips out the OIL LEVEL PLUG.

Smacking my forehead at this shop gem insight I must agree makes plenty of sense extept the dang plug can be bugged threads prior so a bugger to fiddle with and not leak afterwords. Fortunately any over or excess filling just seeks its own level fairly soon, so self educating, self determining after a while.
 
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hobot said:
Put it on the side stand and add fluid to the fill hole till it drips out the OIL LEVEL PLUG.

Smacking my forehead at this shop gem insight I must agree makes plenty of sense except the dang plug can be bugged threads prior so a bugger to fiddle with and not leak afterwords.

Yes, I guess there are always exceptions to the rules, aren't there. I have always found well chewed chum gum to be effective. This is of course for low pressure areas only, like primaries. :lol:

For the sake of arguement, anyone tightening the plug hastefully against the flow of oil, then there is too much oil in there. If overtightening to the point of thread failure then the effect of the oring becomes mute. Such a failure MUST be rather low in frequency. Hobot, does your oil level plug have "bugged" threads?
 
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The primary oil level is purposely to be kept a little below the bottom chain run, for good reasons.
Any more than is necessary to get slopped on the chain is wasted effort and also is more oil that can find its way
into the clutch, which in theory is designed to be dry and has grooves cut in the friction plates to rid of oil.

1) The chain picks up oil just fine as the level changes during riding, every vibration, every bump in the road flings
oil upward onto the chain.

2) As the primary heats up the oil becomes thinner and even its mist helps lube the chain.

3) A chain does not "need" to be dragging in lube: Our rear chains are oiled only every couple hundred miles.
Even the exposed primaries of the Manx racing bike had only a tube with oil aimed at the lower run.
Yeah I know, the chains were changed after every race long TT, but they could have enclosed the primaries and filled them with oil way back in the 20s and 30s when Manx's ruled European road racing.

I think the Norton engineers got it right, fill only to the level plug, 7 ounces is just fine.
 
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I have always found well chewed chum gum to be effective.

Alrighty keep em coming pviss. I've tried anti-seize and teflon tape that's a waste of effort so chewed gum is in the works. Mine don't leak to drip off stopped state but do weep a film over the 'shine'. The 3 covers I've dealt with all had buggered drain threads and screwed up driver slots, so once I got em sealed its preeminent. I just look it to see that lube/ATF is close or touching links. Exactly same situation with gear box too, I never ever take that level plug out and can be a terror to turn w/o buggering the head flats. I glance in the fill hole to see lube level showing deep inside over lowest cogs but not flowing into the outer cover.

There is so little need of primary oil its a non issue to run w/o it a while if not at half way race speeds a long time. Was nice to reason through this a year ago on one of Trixie's initial outings the crank end nut came off to rattle about so opened primary enough to drop it out then headed home 20 miles no problemo no pensiveness after understanding / removing the noise. I put pine needles under to sop up the ATF from staining the paved drive in tree shade I did this at.
 
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