No return on pump

mine took over 5 mins to get oil back to a higher- mounted tank, but didn’t smoke meanwhile. I am assuming the oil supply is slower than for a twin, hence delay.

You have a blockage in the return circuit or a leak where the pump is pulling air instead of oil or the pump cannot prime its self due to an air lock. What work did you do on the bottom end during the rebuild. There is the remote possibility you have the oil pipes connected the wrong way round, I doubt you have but worth checking as its an easy fix.

So you need to check the route back to the tank is free from obstruction Blow some air through or use an oil can to force oil through the case mounting face return hole) and check the pump is mounted onto the crankcase well enough to seal and the pump not be sucking air.

The early single's oil pump return gears are 0.41" in width which is larger than the Model 7 but the same as the 650 & 750 engines.

The only time I experience a significant delay, on my 650, with oil returning to the tank is after an engine rebuild that has included a dry sump and empty crankshaft before running. Even then oil appears within 2 minutes. Less if an  oil filter is not fitted.

In respect of oil flowing well, adding a filter to the system on a twin has two potential drawbacks. If the piping is not correctly connected to the inflow and outflow of the filter then this item's pressure release valve will not work and actually block the flow of oil.

Secondly, it is quite easy, with a filter system, to mix up the feed and return pipes to the oil tank and get a situation similar to that described in some postings above. ie. a sump full of oil, lots of smoke and nothing returning to the oil tank.