Mick Hemmings anti-drain valves

... non return valve part number 6R5-24408-00  from Fowlers Yamaha. Nicely made with an O ring seal rather than a ball. As with all these the key thing toobserve is that the feed pipe directly below the valve is full of oil with no air bubbles. I've used a bit of clear pipe there so I can check easily.

That’s an outboard fuel valve, I assume it allows plenty of feed to the pump?! 

Dan

 it has a 1/4" bore which is unobstructed when open. A lot of Velo riders apparently use them rather than the standard Velo item.

As long as it opens with a gentle blow in the right direction then it should be fine, the steel ball on steel seat ones can stick so having a rubber seat is good. The trick with these valves is to ensure the pipe is full of oil down to the pump every time its disturbed and on the first start of every day you run the engine long enough to observe new oil being returned to the tank. By new oil I do not mean the oil left in the sump from the last run, so you have to look at it until the bubbles appear showing the excess in the sump has been cleared and a couple of mins more to show that new oil is replacing it.

Since the Dutch rally I know of 3 engines that have gone bang due to these valves. 2 were the auto opening type and one was a manual valve that the owner forgot to open after stopping for a cuppa. One of the auto type had worked for 10 years, and then suddenly stopped working, having worked fine the day before. 

If you really need to fit one then consider John's advice, considering the time taken to check oil returning, against how long it takes to drain the oil from the sump in my opinion does not make them worth it. If the bike is used weekly then you will not have a wet sumping issue, if you leave the bike for long periods then either drain the oil or live with the fact you will need to spend 2 mins draining the oil from the sump. 

Didn't Mick 's business get bought out by AN? Maybe they continue with the product. 

Otherwise it looks like you have your answer already...

J

To clarify, AN has not bought Micks business, and no they don't do his anti drain valve.