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I recently noticed a ticking noise coming from #1 cylinder. Think of the
ticking watch on "60 Minutes". The ticking might have been there all along
but only noticeable recently because of some sound deadening projects.

The ticking is more pronounced when the engine is cold, gradually becoming
fainter as the engine warms up, but it never goes away entirely. The ticking
is also louder when accelerating. Ticking is present at idle and higher
speeds with the frequency of the tick relative to the engine speed.

Compression is 150 psi, valve lash is adjusted correctly, and ignition timing is
per factory spec.

Any ideas?

Happy New year.

My suspect would be rocker arms. Suggest you break out you mechanics stethascope (Kmart a few bucks) or a long screw driver with the handle put to your ear and the other end to the following: valve cover, head and cylinder. Where you hear the tick the loudest is where to investigate. I'll bet a couple of Patrick's umlats that it is in the valve cover area.

Piston pin play? Sloppy piston ring?

Worn valve adjusters will give a false indication of correct valve lash... This is where most ticks come from..

Sounds like a possible exhaust leak at the head(blown out manifold gasket), use a hose to listen for leaks.

Sounds like a possible exhaust leak at the head(blown out
manifold gasket), use a hose to listen for leaks.

Looks like Jim LaGuardia takes home the prize... I crawled under the truck
with a flashlight and a stethoscope and found that #1 cylinder has a broken
exhaust port stud.

Fortunately I have a spare head assembly, but have never changed one out.
There's no head gasket, right? Any pointers on a head R & R?

Many thanks,

Jay
Happy new year.

If the stud still has some 'portion" left inside the manifold flange you may be able to remove it without head movement. There are some broken stud "socket style" removers available that work quite well if you use some patience.
We use a copious amount of freeing agent to penetrate the threads then progressively work the stub back 'n forth until it frees off. The stud removers can be purchased form all the good tool suppliers.

If you have to remove the head you will have to strip off the appropriate amount of tin to gain access to the manifold(s) and the head bolts.
Easy to tear down the only thing to take into account is to use new pushrod tube seals and only "nip down the head(s) before installing the manifolds. This aligns the whole lot so that you don't strain the flanges and besides it ensures a good seal on I/Ex flange gaskets.
Once all nipped together then torque the heads. There is a special tool for that job, the Linden method works just as well.

On that rattle business remember the rocker shaft is supported on a two pillar blocks with shims on either side. A common problem on old Brit bikes (like the Royal Enfield) was this rattle since they shared the same set up as a Pinz . Often caused by end float, the pillar block can be adjusted on the studs to eliminate the float merely by loosening the fixing nuts.
Best regards
Dennis

Just drill through the old stud and use an easy out, if you use a Left hand drill bit it may come right out