Early Dominator. Rocker Return Pressure Valve.

Hi Robert. Thanks for showing interest. Yes, I was unaware of this part and only noticed it shortly before fitting it back after the total refurb. Obviously I can't show a photo of it now it's back in. So I do have one but was thinking about the way I fitted it and wanted to make certain I can remember it correctly.

You (and maybe others) might want to fit one, if like you, they have oil shortages to the rocker box. It would be quite simple to make by using a suitable size bolt (head removed) of about an inch long drilled right through and a slightly bigger thread formed only half way through this hole. The whole thing screws into the oil return union at the tank. A small ball bearing is then dropped into the hole (which is tapped in to seat the ball on the smaller diameter untapped section of the bolt) A light spring then added which is held in place with a drilled grub screw (to let oil flow through it and back to the tank)

The action is as follows: Oil returning to the tank is stopped by the ball....the oil is forced to go to the rockers.....as pressure builds in the rocker shafts, the spring is lifted to allow the ball bearing to lift off the seal and pass excess oil back to the tank.

In practice, viewing the return flow via the filler aperture, it is no different to bikes without the valve as the full flow return after starting looks continuous and plentiful, but hopefully, more oil than would be the case without it, is indeed getting up to the rocker gear.

Strangely though, by stopping the flow by blocking with a finger immediately builds up pressure and forces the finger off, so I was puzzled by this and wanted to be sure of what was going on.....I would have imagined that the oil would have been deflected to the rockers as it does on bikes without the valve?

Hope the valve description is of some use and could draw it but only from memory at the moment.

Les

PS...Happy? I guess it's all relative, and you can always tell yourself you are whatever the situation.

PSS Thanks also to Ian .

Ahhh...Thanks very much Les. Yes that's it and my description of it being a separate parts that screws into the oil tank union was wrong....sorry if I misled anyone earlier. The whole union forms part of the valve so it might make a DIY modification more easy perhaps, hard to say without hands on...depends on the bore hole of the union....

Anyway, my '53 twin did have one as standard ...well I thought it was a standard fitment but yes, Roy Bacon does mention that type of valve was only fitted on the Jubilee so it seems the original owner might well have fitted it to give extra oiling up top. I will see if the Jubilee parts description shows this but the Norton Model 7 and 88 parts book does not show the oil tank and fittings so hard to know if it was a standard feature ...Roy could have been wrong of course!

The photo does prove to me that I could not have fitted it wrongly...there can only be one way.

Will attempt to find the parts number and come back on it, perhaps if this was available others might want to use it?

...Many Thanks again.

Les.

Hi Phil and Les...thanks for your info....The valve IS available from ANDOVER NORTON for £13.50 + vat...they refer to it as an OIL RETURN ADAPTOR (WITH FLOW RESTRICTOR) part number 22148. I guess it would be quite easy to call them to actually ask if it was as the photo above shows (my one is identical)..IE: a spring controlled ball valve restriction rather than a smaller orifice.

Strangely, after checking every parts manual relevant for both M7 and Jubilee I still can't find it mentioned or any drawings but at least you can buy one.

If I get time I will phone Andover Norton tomorrow and get back here.

Thanks again on this detail.

Les

Thanks to Paul and Phil again for some more information and suggestions.

It is very odd that there are no factory listings or drawings of the "adapter" but the photo supplied by Les Croston (see repeated photo via link below) is definitely the same device I have. This small pressure operated valve is without question better than any restriction in the return as the valve opens at a predetermined (light) pressure.. As you all know, the rockers are higher than the oil tank return spout so there is no reason that oil should rise up the rocker pipe. With cold thicker oil, enough pressure is created by the outlet pipe restricted nozzle but after the sump is scavenged 50% of the return flow is air that escapes so easily that it doesn't push any oil up the rocker pipe.

However with a pressure sensing ball valve, irrespective of oil viscocity or whether the flow is aerated, the same restriction to the return flow is created to ensure there is sufficient "push" on the oil to get it above the outlet and up to the rockers. Furthermore, should the return oil be cold and thick and pumping fast from a wet sump condition and high revs, it prevents excessive pressure build up on the scavenge side of the pump that a tightly restricted orifice will create. The pressure valve device will keep the delivery pressure to the head constant regardless of conditions and allow oil to flow freely to the tank when large amounts of oil are on the move.

What seems very strange is that this simple, cheap device was never continued to be fitted. It is foolproof. I really cannot think of any downsides to it.

Les

http://www.nortonownersclub.org/noc-chat/technical2-heavy-twins-forum/966632969/166594136/oil-tank-return-pipe-adaptor-jpg

Just spoke to Ashley at "Andover Norton"....what a great bloke, ....very helpful and enthusiastic. Anyway, the item 22148 is now out of stock and was probably a batch of original items and unfortunately no details remain. However, if one could be located for inspection he is very willing to get some made up and has undertaken to locate one himself which I consider to be incredibly generous of him...might be some time but an update will follow.

Les

Previously Bruce Mitchell wrote:

"Curious, I found it on their site (Andover Norton's) and was able to "add to cart" with no mention of it being out of stock. Perhaps they need to update their system so it indicates that before you try to make the purchase".

Hi Bruce...When I spoke to Ashley of Andover Norton he tried to find one and said they were out of stock he commented that they need to modify their web site and computer so it is up to date with their stock level so in fact they don't have one currently.

_____________________

Phil.

Indeed the NOC shop does have one!!. Now the important thing is to see if this version has the spring loaded ball valve....is there a chance of getting in touch with the shop people to check if they are like this please? I don't know what their number is otherwise I would phone them.....Les