Oil not returning .

(1) Crankcase mod: was this the mod detailed here: https://andover-norton.co.uk/files/c39/Combat%20Mods.pdf ?

If so, you presumably also modified the breather (otherwise there's no point to the mod) — but explain exactly how. Did you fit any kind of one-way valve.

(2) Full-flow oil filter?

(3) Anti-sump measures in oil feed? (Tap? Velocette-type ball valve?)

(4) Priming oil feed: did you check feed to rockers?

hello

makes you wonder if the scavenge side of the pump needs priming with a bit of oil 

barry

hello

i only mention it because i reconditioned a rover v8 engine once and the new oil pump wouldnt pull any oil up not matter how much oil you threw at it. i ended up packing the pump full of petroleum jelly. it worked straight away after that .

barry

Maybe he removed the wrong bit.  If he's a 'respected Norton engineer'  he should be able to sort it out. For nothing.

I'm inclined to agree with David Cooper. If you refer to the guide on the AN website (https://andover-norton.co.uk/files/c39/Combat%20Mods.pdf) it may that somehow the scavenge F in the timing side crankcase is obstructed, either by a foreign body or because the material E in the drive side crankcase has not been properly removed.

1)  Check that the oil feed and return lines have not been reversed.

2)  Some oil filters have a one-way valve inside. Reverse the feed and return by mistake and oil will flow from the tank into the engine but not return very easily.

3)  A blocked scavenge caused by a piece of tissue did the same to my 500 twin engine.

4)  Take off the Timing Cover and check the obvious. Is the oil pump worm turning when the crankshaft rotated.   has the Woodruff key been left out?  Has the oil pump rubber seal been left off.  Ditto for the Timing Cover seal.

5) While the Timing Cover is off turning the crankshaft should confirm that the oil pump is working when oil flows from the pump nipple.

I'm sure I read once that someone had the same problem which turned out to be the gasket on the back of the pump was on the wrong way and covered the scavenge side.

Who assembled the crankcases after the 'mod' was done? They could have blocked the scavenge side drilling will sealant.

Timing case and oil pump off and blow through the port, into the case with compressed air. This HAS to be clear

Did you have photos of the case when being modded? i.e. as a check that the mod was done correctly.    

topic will be expanded here:

https://nneno.org/forum/nht-engine-drive-train/629-drive-train-commando

expanded here:

https://nneno.org/forum/nht-engine-drive-train/711-nht200000-d-d-b

My commitment is to continue to write and improve these publicly viewable articles to the best of my 30 years of experience with my own and many other combats. It may contrast with the AN link/article also submitted above

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so was the debris the main cause?