Ariel Owners Motorcycle Club

After a few posts on here regarding a mechanical clang, I finally, and by accident discovered today that the exhaust valve occasionally sticks down, after which it rises up and hits the tapper adjuster with some force, resulting in the clang I have been searching for.

Clearly, the head has to come off. I am assuming the sticking is caused by either wear in the valve guide, a bent valve stem or a lubrication issue.
Will know more tomorrow, but I would be interested to know if, when the valve is stuck down, does the pushrod float somewhere between the cam and the rocker lever. In this state, is it possible that the interface between these components is causing my occasional mechanical jam when starting?

I have re-posted the above from my original post titled - mechanical lock up - w/ng, as the post has moved on.

I'd put money on your 'occasional jam' being the kickstart. It's a common problem and I understand that the fix - replacing bushes, quadrant, or grinding the first tooth is not too predictable.

So far, I've replaced my quadrant but it will still stick occasionally. This is the CP on the W/NG - the BA on the SQ4 is fine.

You will find the valve material pushed up to a ridge becouse the material of the new valves are not mathing with the guids, use an old valve and your problems are solved.

I removed the valve today, couldn't see why it would stick! I then spoke to a retired British Aerospace engineer who does lots of work locally on old bikes. He said that due to years of grinding the valve seats, the stem on the valve at the lower end, where it flares out, starts to bind on the end of the valve guide. I measured it all out, and he is absolutely correct. The part of the valve where it starts to flare, just above that and before the actual stem, the diameter increases by 0.050". This part is just exiting the valve guide.
The solution is to countersink the final part of the valve guide, which I have now done. Once its back together I will update as to whether it was successful.