Hitchcocks Forum

Morning all. My recently recommissioned 1944 WD/CO has done roughly one hundred miles now, and it's taken to spewing it's engine from the breather. The engine had been given a glaze-bust and new rings, new cork oil seal on the crankshaft quill, and on the advice of the original RE workshop manual, the scavenge pump disc has been lapped in with metal polish. The filter is also new and the rocker pipe is clear. The return to the tank isn't a "spurt" but more a gentle ooze from the orifice. The bike starts first kick and pulls like a champ, and the plug is a nice chocolate brown (not oily) colour. Something's fundamentally wrong here as the engine would lose all it's oil in ten miles, so any pointers?

Hi, check the return filter under the sump (big nut toward the front of engine) this may be bunged up with crud. Vince

Hi Vince, I should have said that both the filters have been washed and blown clean.

Should be an intermittent spurt. Sounds like the oils not scavenging properly.
Don't forget all the oil returns via the head so make sure there's not a blockage up there. You might disconnect the rocker feed pipe and see what the flow is like there.

How do you mean "the oil returns via the head"? Also what is the purpose of the so-called non-return valve situated in the filler neck?

I mean ALL the oil which is delivered to the bottom end of the engine and ends up in the sump is then pumped up to the rockers and then drains down the push rod tube into the timing case and then to the tank. This is different to most designs of the period where only SOME return oil went to the rockers. I partial blockage on the scavenge circuit will leave too much oil in the sump and will blow out the breather. Don't know what you mean about a ntv on the filler.

Hi Pete, there's a non return valve situated in the oil filler neck; it consists of a screw-in brass plug, a spring and ball. Your assertion that all the oil goes up to the rockers etc isn't borne out by the oil flow diagram and explanation in the official 1947 RE workshop manual. In actuality all the oil is scavenged back up into the oil compartment other than a small amount diverted up to the rockers by the NRV mentioned above. At least, I'm thinking that's the sole reason for the NRV, I just wanted confirmation. I have read the "all the oil...etc" theory elsewhere but maybe it applies to later bikes only?

Hello Tman,

The prv in the filler neck, as far as i know, is to protect the oil pump worm drive from excess pressure when the oil is cold, or too thick an oil is used. Most of the oil, when hot, goes via the rockers. My Clipper is a similar system and oil just oozes out of the valve or comes out in small spurts.

Tman I think you're reading it's purpose the wrong way round, it's not a non-return valve, it's a pressure relief valve, also a long term feature of Redditch designs.

REgards, Mark

PS,
I check the dipstick oil level sometime after returning from a run, rather than before using the bike. If the join between the crankcase halves is not perfect, the hot thin oil can leak from the tank into the crankcase causing the reading to be low. I didn't realise this the first time and topped up the tank, went for a ride and after about eight miles, oil was dripping out from below the ignition drive at the vent hole - which is where i think you mean yours is leaking? The return pump had cleared the excess from the crankcase and overfilled the oil tank.
This might not be the fault you have but if you are checking the oil level before a ride and finding it low, this could be the reason possibly?