1954 NH first proper shake down rides

[paul.jameson]

You didn't say whether it is an Ariel oil pump or a Morgo one. The reason I asked is because the extra flow from a Morgo pump could be enough to overfill the timing case.

Are the clutch plates flat, especially the plain ones? A kitchen worktop is good enough to test them on. It might be that the best answer is some new plates with corks from Geoff Brown - and the nice light springs to match.

[Gui.dorey]

It’s the original Ariel pump. I just cleaned it, tested it and reinstalled with a new gasket.

I also checked the plain plates for flatness and they were ok.

What is odd is the clutch hub. This bike seems to have been well used as witnessed by some of the repairs and some non original but period parts. The clutch centre inner splines don’t match the ones on the mainshaft sleeve, or rather they match exactly but tooth on tooth ( hard to explain, but I don’t have a photograph - I’ve attached a sketch). Let’s say the inner diameter of the clutch centre teeth just slides over the outer diameter of the teeth on the mainshaft sleeve. Whoever the clever mechanic was, solved this problem by making individual keys that fit precisely in the gaps created between sleeve and clutch centre. It works, but I do realise there is something here not quite like Burman did it. Otherwise the clutch centre looks like the right one and has the raised edge at the back against which the first plain plate presses on. Ever seen anything like that?

[will_curry]

The ingenuity and ability of Ariel owners never ceases to amaze and sometimes
amuse me.

A 2-plate clutch centre has 7/8" of spline before the shoulder for the plain plates
to sit on and the diameter of the splined part where it sits on the mainshaft adaptor
is 1"3/16.

[paul.jameson]

I echo Will's comment on ingenuity.

I have a used 2 plate centre spare here which you can have foc to try if you would like to. Its far from brilliant but is probably good enough to prove whether or not that is your problem. PM me if with your address if you would like me to send it.

On the oil problem, I can only conclude that your modification to raise the oil level in the timing case has raised it too far in the magneto chain case. Quite why is difficult to say but the timing cases on singles have many variations. Some of the less obvious variations involve changes in the drain hole heights so it may possibly be that your timing case is incompatible with the modification. I appreciate that it would involve re-timing the engine but I suspect that trying the bike without the timing case modification may be the next option to try.

[Gui.dorey]

Hello Paul,

Many thanks for your kind offer, and I shall send you a PM. I‘ll cover the postage costs of course as I‘m not in the UK

Regarding the modification - actually I had the exact same problem before the mod, and I did the modification in the hope of solving it. The modification made no change whatsoever - the leak remains and the amount of oil going through to the mag didn‘t even decrease. Interestingly, there‘s a chap from Italy on one of the Ariel groups on Facebook with exactly the same problem…
https://www.facebook.com/groups/2809984 ... 899872267/

[paul.jameson]

It occurs to me that a quicker option for you would be to try the clutch from your Mk I. You will have to remove it anyway to strip the engine and it will fit straight on to the NH, despite the different gearboxes. Another thought is that the strange arrangement in the splines might be replicated in some way in the needle rollers for the clutch chainwheel - perhaps some are missing which would make the clutch basket wave about somewhat.

I have to admit to being fairly well baffled on the magneto over oiling issue. Clutching at straws, the short breather pipe could be the problem as oil goes in all sorts of strange directions due to air flow as you travel along. I once had oil appear on the top of the glass of the speedo on my previous Healey and there was no oil within 3 inches of that - but the airflow took it there. The only other idea I have is whether the oil line to the big end could be blocked, either by a full sludge trap or fitting of the big end the wrong way round. A blocked oil line would cause the oil level to build up in the timing case until it overflows into the crankcase where splash will keep the engine running ok for a long time.

[Gui.dorey]

That‘s a good idea Paul. I did‘t think of my Sq4. However, the MkI has a 3 friction plate clutch, so I would have to use the centre AND the basket, correct? Will the NH‘s clutch push rod still work, or will it be too short? What do you think? The rollers are all there. I had the gearbox and everything apart for cleaning and inspection, and the only thing I found was this ingenious assembly for the clutch centre. I‘m still wondering where that centre comes from…

As far as the oil in the timing case, I‘m also clutching at straws. All your points are valid, but I‘ve been through them. I cleaned the sludge trap and all the oil passageways when I had the engine apart (I believe I even posted a picture here of what I found in the trap. It was full to the brim!). After the first longer ride and noticing the leak, plus some wet sumping, I took the oil pump out and cleaned the balls again, plus checking all passageways to the cranks and big end. All was clear. The return to the tank and flow to the rockers is also working as it should. I have a small leak at one of the rocker‘s banjos so I know oil is getting up there.

I will try attaching a hose to the breather tube to extend it further dow as Will suggested to see if it improves things, but by the amount of oil getting through the Mag, I would be very surprised if it works. I‘ve also thought if maybe the pump itself has an internal leak. It is the original and maybe it is worn or distorted? Who knows… I might try running it with the timing cover off to see if I notice anything.

[paul.jameson]

Once you remove the clutch centre, its only 6 bolts to remove the basket. You will probably have an issue with the pushrod length but adjustment might be possible if you are lucky. If not, get a length of rod - preferably stainless, cut to size and use that. The lack of hardened ends won't matter for tests of a few miles (and some of my bikes have been running stainless pushrods with un-hardened ends for thousands of miles). Whilst writing this, the thought has struck me to wonder if your clutch centre is for a 3 plate clutch but with 2 plates it is holding the pressure plate almost clear of the other plates.

I will post later about the oil problem - I have a theory but it needs research to see if it is a runner.

[paul.jameson]

On the oil problem, I have checked to confirm my suspicion that the breather on the drive side of the crankcase was fitted from the year of your bike, 1954. Does your bike have this breather fitted or has it just the one on the back of the timing case? Could it be an early 1954 example fitted with 1953 style crankcases? Just a thought.

[Gui.dorey]

Hi Paul,
The clutch centre must be a 2 plate one as I tried to assemble more plates and they don‘t fit. I shall take some pictures and measurements the next time I‘m in there.

I do have the crankcase breather and it is also clear and free.