Ariel Owners Motorcycle Club

Put the original sized pump in and you should have no trouble. My hard worked 41 model has done about 15,000 miles since I started using it in 1997 and never blows smoke even without an oil ring. After about a minute the return oil should become intermittent if everything is normal. Nev

Some progress at last. Drained the sump of 300ml of oil, started first kick, no white smoke and spurts into oil tank rather than a continuous flow.
So I now know a lot more than I did 2 days ago, specifically, lots of things that are not the cause.
I have the left the sump off with a container under to see if the oil is draining back into the sump. Ill leave it overnight to see. Bearing in mind I rode 850 miles this year without any white smoke, it begs the question, why?
I am leaning towards detritus under the ball bearing in the oil pump; there was evidence of this as when I took it off, there was a very poor 'pop' on the scavenge side, which improved with cleaning.
Failing that as Nev says, perhaps I should fit the smaller period oil pump; but something must have changed for that to be the reason. Maybe the new head has changed the dynamics of the oil flow in some way.
It is a relief though to hear her running nicely; what a lot of rabbit holes I went down!
I will keep you updated, but big thank you for all your replies and help.

The rocker boxes drain down the pushrod tubes. I suppose one of the rubbers
could be the cause but I can't think how at the moment. On the later engines
with enclosed pushrod tubes I've had real problems with oversize rubbers
further swelling and crippling the pushrods as well as flooding the top end. Grrr


@will_currie - Sorry to be a bit 'off topic' but have you seen this mod for the later motors ??


I have done this and it appears to work for my '58 VH with an aftermarket alloy barrel !



Bob.

That's got to be debris in the pump valves I think. I can't see how the pushrod tubes could get blocked on the early engines.

There is a small part of the 4-stroke cycle where the plungers are as far 'up'
as they will go and the ports are uncovered. If the engine stops in this position
and the valve on the delivery side is not sealing properly there is a direct path
from the oil tank to the sump via the big end.

I don't think the scavenge side can be defective as there is a continuous return
to the tank. When that valve is leaking nothing gets back to the tank.

Bob:
Yes, I've seen the threads and I have something similar which I believe came
from Ariel fitted in my HT. The problem only arose because I used a very poor
pattern part available many years ago and after I had used up my supply of
original Ariel seals.

The balls in the valves can wear out of round. This will give an intermittent problem. The tapered spring works best. I wouldn't use the others. They can bend. Nev

I think I may have found the smoking gun. I ordered new springs and 7/32" balls for the oil pump following advice from Nev. So this morning, I removed the pump and out of curiosity, I tested the plungers using the 'pop' method; nothing on the delivery side, no resistance whatsoever. This is odd as when I did this a few days ago, it was fine. On removal of the balls (which incidentally where 1/4"), I found a tiny shard of metal sitting in the seat; was about 0.0040 and 0.0020. The smoking gun. All back together now and starts and runs as she should. I expect Will's explanation above is therefore correct.

Whilst I have your attention: When I removed the previous cylinder head and dismantled I noticed that the diameter of the inlet valve was much larger than it should be. The valve guide was also the same size as the one for the exhaust side. It did look like the inlet valve stem had been ground down at the top and the chamfers added. I can't decide whether a larger inlet valve was fitted to improve performance, or whether it was done because that was all a previous owner could obtain?

350 parts have always been fairly easy to find, especially compared with 500 parts. So my guess is that either someone was aiming for improved performance or just possibly that they accidently bought a 500 inlet valve and guide and fitted that. The 350 exhaust guide is the same diameter as the 500 inlet guide. The bike wasn't previously owned by Ross Davis by any chance was it? He had a ridiculously rapid W/NG.

The previous owner never used the bike Paul, but he bought it from a soldier based near Swindon; sorry, but I don't know his name.

It wasn't Ross Davis then. Ross was overseas membership secretary for many years and lived in Wellingborough, Northants. But his W/ NG went like stink.