I chatted to Nick at Andover a few years ago when they were looking into getting these made. They go out of there way to make their parts the same as the factory drawings and leave the modified parts to other after market sellers. I know they'll be good quality. I lapped in my 16h old oil pump but it still wet slumped, so I fitted a valve. I'm not sure why people are against them when they were fitted to Velo's as standard. The valve I've got screws into the crank case so is as near the pump as possible. The advantage of the 16h is the oil pressure indicator so you know the valve is working. I've also got one on my ES2 and even when left for a long time the valve has never got stuck, but a quick check in the oil tank will show the oil in returning.

You can just see the valve in the crankcase.

email (option): horror@blueyonder.co.uk

Must admit, I've never found a gear pump which will stop 'wet sumping' - they are simply not designed to seal - however well made they are.

As for inline check valve - no reason they shouldn't be reliable if the oil is clean.

At least the 16H does have a positive indication of oil flow - my '32 ES2 has the original stop-cock/valve on the oil tank and yes i have have forgotten and went something like 5 miles before i felt is slow - quickly remedied by opening the above valve!

At the beginning of this year i felt she was nosier than normal (6th sense really) and discovered the indicator barely lifting.
It turned out the fiber-seal/washer between the cam-cover and the crankcase had failed and little oil was going down the crank-shaft. Again easily enough solved.

With this warm summer - discovered that again the indicator was hardly lifting ..... check above seal, etc. then remembered she was using 20/50 (she usually gets driven in winter) and changed to a straight 40 grade - problem solved.

I do now check the indicator when i set off and at various times on a ride - a handy device.

The pumps for the Norton twins (which have reversed gears compared with the singles) have never really been out of production but quality through the 1970s / 1980s was pretty indifferent and a new pump often little improvement in terms of draining down when compared with an obviously damaged example.

I've been using one of the more recent Andover examples on a Commando for some years now and find it to be a big improvement - months rather than weeks if it's standing still while the 16H is getting all the use.

The singles pumps (WD at least) were mazac bodied with the attendant ageing problems. The current production follow the twins practice and are steel which bodes well for longevity.

The lack of filtration on a WD16H probably does mean that wear will be faster than on a later machine with cartridge filtration.

Well, I bought one, I'll let you all know how it works out! :-)