anti-wetsump valve

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Apr 15, 2004
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I bought one of those inline anti-wetsump valves. It has a ball bearing and a light spring inside, "based on the Velocette design" according to the ebay merchant I bought it from.

But I've noticed on the UK NOC site there's lots of horror stories about people who fitted similar valves then blew up their motors from lack of oil. Now I'm nervous. Are my fears groundless or am I flirting with disaster? I poked a wire inside to test it and it seems to work fine. Spring action feels nice and light as they say it should be.

Perhaps fitting an oil pressure gauge at the same time would be a good idea? Then if I start the bike up and have zero psi I'll be able to detect the problem before the damage is done (?)

I've heard those rumours as well. If the valve sticks it could result in serious engine damage. By the time you've noticed the low oil pressure on your guage I expect the damage would be done. One way to work around this is to fit a tap to the oil feed linked to the ignition so that teh bike cannot be started when it's closed.

Or, here's the view of the Norvil company in the UK:

Wet Sumping Solved

Your Norton Does Not Need To Wet Sump

Many people are turned away from owning and riding classic bikes, especially Nortons, because of the problem of oil leaks and wet sumping. Well, I can tell you here, no word of a lie, my 650SS does neither. Wet sumping is an issue many riders have found with their classics. There are four simple steps that have been followed to eliminate that potential problem on my 650SS. When all are used together, your problem should be solved forever, meaning more time can be spent riding your bike rather than emptying the sump and refilling the oil tank.

1} Firstly, you need to use the correct Monograde oil (SAE 50 in summer and SAE 40 in winter).

2} Secondly, you need to leave your pistons on compression, to do this, slowly press down on your kickstart about an inch or so, until it reaches the top of the effective swing. This has the effect of raising your pistons and the big end journals to the top of the barrel and so oil has further to go before it can drain out.

3} Thirdly, some Norton's can have an anti-drain valve fitted inside the timing cover, (AFTER the oil pump), this prevents the seeping of oil down onto the bottom of the crankcases. On Dominators & Commandos Pre 131257, a modification can be made to your timing cover, if you send it to us, (see workshop services code WB12). On Commandos with engine number 131257 onward, a new timing cover, (066161A), can be fitted to solve the problem - see picture below. ** PLEASE NOTE ** This is NOT the dangerous type of anti-drain valve, which is fitted by some people into the oil feed line above the crankcases. Anti-drain valves fitted into oil feeds, always cause oil starvation to the big ends for a brief time when starting the bike. If you use a tap instead and forget to turn it on, it will totally blow up your engine).

4} If the above three steps have failed to solve your problem, then you probably have a faulty oil pump. Oil can flow backwards through the oil pump if it is in need of attention, most oil pumps can be repaired and restored quite simply – mine was. The fourth step, is to have o-rings fitted to your oil pump shafts to stop oil draining from the feed to the scavenge side.

Good luck sorting it out.

Debby, From what I have seen most problems with these come about when they are first put in. The system needs to be primed and tested. It does make sence that if they are used to cover the oil pump leaking that all the line oil after the check valve would drain away. This would made the problem of start up wear become a every ride thing. I don't run the in line valves on any of my bikes. norbsa

I truly think the "wetsumping" thing is overated like the "boyer problem".

Maybe some oil pump tolerances weren't as good as others & with the right maintenance, it should not really be an issue.

With the 7 nortons I have owned is hasn't been an issue. But maybe I was lucky as with my boyers.

Possibly a "better" oil pump will help more than an "anti-drain" valve :idea:

Whatever makes u feel comfortable in the end.
Anti drain valves

G'day, I'm new to this list but have owned a number of Nortons over the last 20 or so years with my current ride a MkIII Commando.

My last Mk11A, which I owned for 8 years and sold about 3 years ago, blew a crank seal due to wetsumping, so I fitted the same type of anti drain valve (Velo type). I ran that bike for around 5 years and probably close to 30,000miles with the valve in without incident. It was simple to fit, I made sure that oil was returning after fitting and never bothered about it after that. I have also heard the horror stories but strangely have never actually met anyone who has suffered from the oil starvation problem after fitting one. Wasn't a common problem for Velo owners so why should it be for us?

My 2 bobs worth anyhoo.

Interestingly ever since I restored the Commando, wet sumping has been a 'slow' ~ problem.
But recently I once again started to use Penrite 40 as recommended by The Norvil shop and Les Emery.
I also endeavour to always raise the pistons/ crank to the topof the throw as recommended.

The wet sumping has been even further reduced by the Penrite, so I fugure it is a fairly low profile problem.

I generally check the oil level and if it has dropped any degree of concern I crank the bike up and run it to just get it back up..

Perhaps I will get around to "Dyno Daves' cure.. but it is a low concern rating to me now.. (If it drops that low I will drain the sump before starting the bike.) 8)
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