Ariel Owners Motorcycle Club

The gauge shows you, that the pump is working. Nothing else. It is just to keep you comfortable.
You can never build up a pressure against a roller bearing.

Just looked at the regulator or where it should be and on my machine it doesn't seem to be as I expected. Basically there's a threaded stud coming out of the case with a central hole where the oil comes through. A banjo fitting slips over the thread and is held in place with a capped nut. There doesn't seem to be an adjuster. Thanks Again

My understanding it is there to show that the pump is working .

Mark,
Does your feed pipe also feed the rockers or does it just go to the gauge? You should be able to check the gauge works by removing the pipe and blowing down it, you should see some movement on the gauge if it is ok
Can you post a photo of your setup?

Hi Alan - Yes the pipe just feeds the gauge. I've taken the pipe off and blown through it, seems clear. I'll try it connected to the gauge and post some pictures. Thanks Mark

As Knud says, with a roller big end the oiling relies on volume not pressure. This is my understanding of how it works (sorry if I am teaching Granny to suck eggs):

When there are shell/white metal big ends the gap between the crankpin and rod eye are very small and the pump can build up pressure in the oil circuit. That is why these systems have a Pressure Release Valve which...well.. relieves the pressure at a set PSI, otherwise the pump would be put under a lot of load/stress.
With roller big ends the gaps are large and the pump cannot build up any appreciable pressure so it is the volume / amount of oil flowing that counts. The faster the engine is running the greater the amount of oil flow. As the pressure in the roller bearing system is quite low then, for the gauge to show any sort of reading, there is a need to create pressure in the part of the oil circuit where the gauge takeoff is located.

On the Ariel singles we are talking about there is an oil feed gallery which leads unobstructed from the pump outlet to the rocker feed/gauge takeoff. The rocker feed pipe leads to the rocker shafts which have close fitting tolerances so, like a shell bearing, they allow pressure to build up in the feed pipe. The gauge feed is a closed system so again allows pressure to build up.
At the end of the oil feed gallery is a hole which is blanked off by a ball bearing held in place by a spring loaded piston, in essence a valve. This valve allows pressure to build up in the oil feed gallery and the rocker / gauge feed pipe. It is this pressure that is indicated on the gauge. The spring pressure of the valve can be increased which increases the pressure in the oil feed gallery and rocker feed pipe. Once the valve opens oil flows through drillings in the timing case to the quill and crankshaft to the big end. As we have a roller big end no 'pressure' builds up in this part of the system, and once the ball valve opens the amount of oil flow is not restricted at all in this part of the system.

The rocker shafts only need a small amount of oil so the pressure does not need to be high, hence the 10-15 psi setting, which I think is the 'normal running' pressure rather than tickover pressure but don'y quote me on this. Later models and other marques take the rocker feed from the return side of the pump which only produces sporadic oil flow so their flow rate is not high.

Any comments on my understanding appreciated if I have it wrong.

Mark: I think you need the regulator valve to produce any appreciable pressure in the gauge circuit. Once you have posted the pics we can see how its been plumbed up and the type of timing case you have fitted.

The roller bearing doesn't need much oil at all but that is one way to get some to the piston and the rest of the engine. The rockers need a little pressure to get the oil to them but not much as shown by the later singles that get it from the oil return line.
Prewar the singles had an adjustable ball relief that made the gauge read a higher pressure if you were silly enough to set it that way, because all it does is overload the pump and if it is worn reduce its output. Your oil gauge on a single serves little purpose except to tell you the supply pump is (sort of ) working. If the pressure drops off at low revs unless you ball valve is leaking the pump is possibly not pumping anything at that time. Nev

I think your timing case may be from rather later than 1936, which would explain the lack of a regulator. Perhaps a photo or two would aid identification.

Hi Everyone here are some pictures of my set up the banjo? union obviously isn't attached. Thanks Mark

As Paul says it looks as though you have a 1941 onwards timing cover fitted. There is a supplement to the earlier models in the AOMCC document repository which states that from 1941 onwards the oil pressure valve is located behind the pump in the oil feed to the crankshaft. It is not adjustable but it works on the same principle as the earlier one i.e. it has a seat and a spring loaded ball bearing and is there to produce pressure in the oil gallery feeding the . It may be a case that the spring has lost it's tension, the seat is leaking or the valve has not been fitted. You would need to remove the pump to check if it is there and in good condition.