Norton 50 1957

The usual mantra is overhaul the  pump or renew, leave the motor on compression or fit a tap/ nonreturn valve. My take on the subject is , good to overhaul the pump anyway to ensure engine life , even better have a proper engineer do it. If possible improve the crankcase  breathing to allow the motor to expell excess lubricant back to the tank on startup. Ride it more . Are you using 40 or 50 SAE oil ?. 

I drain the oil if the bike isn’t going to be used for a while, then put it back when required. The Velocette type suction valve works perfectly on my Velo, should be ok on the Norton but the oil line must be airtight and needs to be primed whenever disturbed.

John

While the bike is standing 20/50 is really 20.  This will run faster thro the  pump gears than a 40 or 50. 

Multigrade gives better lubrication to shell big end bearings when warming up.  Monograde is fine for the Model 50 with its ball bearings, because immediate lubrication on cold startup is not so critical as it is with Norton Twins.

It will still wet sump with monograde, but not so quickly.

A new pump will be expensive and may not "cure" the problem, just make it  slower. 

....of my '61 ES2 there was an anti-sumping valve built into the timing cover. It doesn't show in the parts list drawing but there is a spring, ball, and cup listed. This is not the pressure relief valve which is shown in the drawing.  That bike never sumped up, even after sitting for years. When was this introduced?

Hi Michael.......are the parts you highlight the Singles version of a pressure relief system? But in this case using a ball and spring (singles) instead of a piston and spring (twins). The 1959 parts book shows a diagram of the single with the relevant parts marked with B100 & B101,

...seems to have first appeared in 1957 with the major redesign.  When I put my now-gone ES2 together back in the early '80s I puzzled over this and reasoned by the oil pathway that it was an anti-sumping feature. A dim memory and perhaps mistaken.  Maybe someone has one apart now to confirm.   

https://www.nortonownersclub.org/node/13089

and have to say that it worked for me.

Andover Norton list new oil pumps for singles,  but I’d have a good look at the existing pump first, a new pump will still leak through, just a bit slower.

John

Even with a new pump, you will find that the clearances still promote wet sumping. I have found the new pumps are made with a clearance of a thou or two too wide. They are easy to turn by hand. 

When a pump has had its clearance closed up properly you will find it quite difficult to turn with the fingers, not seized, just stiff to turn. This is intentional and is outlined in the overhaul notes in the  (commando) manual. Also a new singles pump comes with the Mk3 commando oil pump feed bush which is too big in diameter ( need to fit the smaller feed bush) 

The fibre washer on the oil pump outlet can also contribute to leaking. Replacement with the later rubber oil pump seal (06-7510) and machine the timing case to match sorts that out. 

Doing all the above won't stop it wet sumping, but it will cut it down considerably. Due to the infrequent use of these machines now (sunny dry Sundays and the like) Unless the oil tank is drained after a run out and filled before next use you must expect wet sumping to occur.

Fitting a valve in the feed line to shut off the oil tank from the engine is possible and indeed loads of owners do just that. That is fine and dandy until it gets forgotten and the resultant blow up can be spectacular. If fitting a oil tap/valve make sure it has an ignition cutout facility. (engine won't start unless valve open)   

...making the onboard antisumping valve work. As mentioned, it will work well if it is clean and intact. A downstream valve (from the pump) is far preferable to upstream and won't fail closed.