Ariel Owners Motorcycle Club

Good evening all

I have a 1937 500cc OHV single Ariel and I ma struggling to get the exhaust valve lifter to operate correctly. When I set it up, the lifter cam that operates on the valve tappet seems to lift the tappet but then get stuck and not return to the 'closed' valve position.

I have looked at the Draganfly website and purchased a couple of spares - the fibre washer for the lifter to rocker cover joint, a new 'crinkly washer' and O ring seal. When I removed my lifter form the engine, it had a spring between the actuating arm and the rocker box fitting.

I am not sure what angle the actuating arm should be at when the lifter cam is just touching the rocker arm?

Are these things a bit fiddly to set up correctly or am I missing something?

Any help or thoughts gratefully received.

hi i had a problem with the valve lifter spring on the cable not pushing the arm right back i had to play around with the arm and lifter to get it working right

A 1937 500cc OHV would be expected to have an open valve head but you may have the later enclosed valve head fitted (as I have on my 1937 500cc OHV). The open valve head makes the valve lifter more difficult to adjust because it is less accessible.

Fundamentally, you unscrew the nut, prise the operating arm off its taper, adjust the shaft by means of the screwdriver slot in the end and tighten everything up again. The trick is in the shaft adjustment. Too loose and you won't lift the valve. Too tight and at best you will get rattles, at worst you will hold the valve off its seat. Wear in the shaft makes adjustment more difficult and wear in the lifter pin on the end of the shaft or wear on the lifter tab on the rocker arm will make adjustment much more difficult.

It does sound possible that your lifter pin and lifter tab are badly worn which might allow the pin to go round the end of the tab instead of pushing it down.

Photos and information whether it is an open or an enclosed head would help to improve the advice I can give.

The lifter is like a model aircraft engine crankshaft and has to come towards the engine far enough to engage the Rocker fully but not foul it. It's all a bit Heath Robinson really. Success rewards diligent application and adequate persistence,.Nev

Thanks everyone for their input - I shall reassemble with some replacement washers etc and try and set it up. I will take a couple of photos of it off the bike, I did wonder if the lifter was worn and so causing it to be able to move too far around.

Regards

Graeme

Afternoon all, having played around with setting the lifter against the rocker and tweaking the angle of the actuator arm I have managed to get the valve to open a fraction enough to decompress, this may be enough though I am concerned that the lifter cam is engaged on the rocker arm permanently!

Please see photos attached of the head and the valve decompressor, I would welcome thoughts on if it is significantly worn, there is a little 'play' when I actuate it.

I have a bronze head on it, which I believe is closed - there is a rocker cover over the top of the push rods and on the valve gear.

Thanks for all your help

Regards

Graeme

Has the valve end got a cap on it? The valve seems too short. When the valve is 1/2 open does the valve axis meet the contact point and pivot point at a right angle, 90 degrees? Nev

You have what is known as an open valve head, correct for 1937. Looking at the valve gear for my 1937 open valve head I see no obvious difference in the amount of wear which should mean it should be possible to adjust your valve lifter satisfactorily. But Nev's point is very relevant. A bronze head and rocker side plates drilled to resemble swiss cheese tell us that someone has been tuning the bike. They may well have fitted a non-standard exhaust valve which could be shorter than standard, hence Nev's question about the valve stem end cap which if present would effectively lengthen the valve stem.
The other possible item to question is your valve lifter cable. At the Long Distance Run last weekend we had trouble with another 1937 open valve gear 500 being reluctant to start. I found that the valve lifter lever had to be pushed much further round to lift the valve than I would have liked, suggesting that the cable inner is too long. If you are operating at the end of the adjustment of the cable, it might well contribute to your problem. I don't know whether the valve lifter cable for an open valve head is different from that of the far more common enclosed valve head but that could possibly be the case and explain the long cable inner on my friend's bike. On the open valve head there is a cable adjuster under the rocker cover which is difficult to reach but may give you the adjustment you need. An alternative might be to fit a ferrule similar to that on the twistgrip to effectively lengthen the cable outer.

Thanks all

On the point from Nev about the valve cap - I don't think I have one on there which might explain why the tappet adjustment on the exhaust valve screws down a lot further than the intake! I shall go an investigate further and take some more photographs.
By trial and error I have managed to adjust the decompressor so that it just enables me to go over the compression stroke, however, I have no valve clearance - the recommendation in 'the book of the ariel' for OHV 1932 to 1939 singles is no clearance cold, though this feels a little unusual to me!
I havent run the engine like this yet (mainly due to the fact I have had to rebuild the carb and repair the fuel tank)

I will add some pics of the exhaust valve and general head.

The help from everybody here is very much appreciated.

Best regards

Graeme

It also helps if the valve lifter is in line with the adjuster, so that the cable doesn't become kinked when you push the lever. I believe that the valve lifter for the open head is slightly different from that for the closed head. The nut on my valve lifter for the open head is narrower and the spindle shorter. You have the longer spindle. I assume that it should still work, but I tried the longer spindle and then returned to the old own spindle. But it should work even without the volute spring. If the pin is at the twelve o'clock position when it opens the valve, it will never come back. If that is the case, you need to change something in the valve gear. It is sensible to check the geometry of the valve gear first, i.e., whether the adjuster is centrally over the valve stem and in line with it when half-open. There is no point in adjusting the valve lifter if you later need to modify he pushrods, valve stems, cam followers etc.