850 Timing Cover

You might be interested in this thread â https://www.nortonownersclub.org/noc-chat/technical4-commando-forum/417983147 â where a possible all-round solution may be brewing. I'm waiting on that, supposing Mr Holmes is still on the case!

The MK3 anti sump is a bit big and miss, partly because of the use of a plunger instead a ball ( just read the thread that's currently live on a plunger stuck in the gallery) plus nothing was done to the oil pump. If you do fit the MK3 cover you need to also change the oil routing in the crankcase.

Thread on jammed plungers

https://www.nortonownersclub.org/noc-chat/technical4-commando-forum/863605755/view

This modification applies to the Norton Commando models through 1974 that from the factory, had the discharge point of the pressure relief valve relocated from directly into the sump, as was the case with the previous Atlas and Dominator models and the later MK3âs, to the feed line from the oil tank. This allowed in many cases, oil to pass through the pressure relief valve in the timing cover, into the sump when the engine was not running, thereby adding to the wet-sumping problem. Our modification places the discharge point back to its original point, directly into the sump, and requires that the oilway from the feed line in the engine case be plugged with a set-screw that we can supply. It is recommended that the threads in the case be cleaned with a degreasing agent such as carburetor or brake cleaner, and then a quality thread-locking compound such as âLoctiteâ be applied to the screw. The screw should be threaded in to below flush with the gasket surface, so as not to interfere with the sealing of the timing cover.

Pictures in this thread

https://www.accessnorton.com/NortonCommando/is-this-part-of-the-amr-nortec-pressure-relief-valve-mod.24205/#post-356456