Good Day Everyone!
Through my various posts and the generous guidance I've received I'm moving along confidently on the varying issues with my C11G.
You all have given me advice on British fasteners (Whitworth vs. cycle thread, etc.), basic must have spanners & sockets and how to execute a 12V conversion which was associated with my needing to do a  complete re-wiring of the bike. I've been successful with each as a result of the support given me.
It's time for the motor.  And more specifically the valves.
As a part of my preparation to attempting an initial startup I wanted to check the valve clearances.  It was immediately apparent that there was an issue.  The intake valve adjustment is so far out of spec that the gap cannot be made up even by fully screwing down the tappet.
Here's what my investigating has turned up so far:
Both valve rods are of equal length and not bent
Both valve rods are installed correctly in that they are crossed and ride up and down with the engine rotation as they should.
For purposes of determining just how far out of whack the intake gap is I set both tappets at an equal height... and the intake gap is probably 1/3" 
When viewing the valves from the left side of the bike they appeared to me that the top of the intake valve was lower than the exhaust valve - and thus the oversized gap.
Going with that, I removed the head and did an unorthodox test.
I leveled the head on my bench.  Checked the accuracy at two points.  One being on the upper most fin and again at the top of the head where the valve cover gasket would sit.  Both nice and level.
Then I laid the level across the top of the valves to verify what I believed I was seeing and sure enough, they are not equal heights.
I know I'm going to need to remove it for further examination and I'll be needing to purchase a valve spring compressor tool to accomplish it.
So, finally the questions.... what am I dealing with here?  What should I expect to find?  Where is this valve journey taking me?
Check out the pics....

FOOTNOTE:  I've been looking at sourcing a new intake and exhaust valve.  Intake part # is 29-2124 & exhaust is 65-208.  BUT, I've read that they're interchangeable?  They're actually the same?

Often there used to be little hardened caps on the top of the valve stems......Have you got one missing?  Ron

No Clue!  They look identical to me... except for their respective overall heights.  Blowing up the picture I don't see any difference.
And I don't know how that would affect the overall height of the unit

Well you might as well remove them for checking, de-coking. lapping in. Ron

Yes, I agree that they need to come out.
Never having done this I thought perhaps others have seen this issue before.
Eventually the root cause should reveal itself but if others have seen this it would give me something specific to zero in on if the issue isn't obvious.

Good Morning Owen -
The bike was purchased as a non-runner.  I don't know when the last time it was ran.  There is obvious evidence of "work" having been done whereas the piston has been de-carboned and the intake valve is basically spotless, so I'm assuming it's either been cleaned (unlikely since the exhaust valve hasn't been cleaned) or replaced as you mentioned.  At this juncture that is my theory and when the spring compressor tool arrives I'll pull both valves and compare stem lengths.  BUT, I have no way of knowing if they're possibly both wrong  .
So that's why I've been poking around for possible replacements to begin fresh and that's where I found claims that both valves are the same regardless of having different part #'s.

Hi,
Looking at the photos posted it appears that the inlet valve is sitting lower in the spring cap ?
So either a shorter valve stem or worn / wrong collets /cap ?
Although the valves are identical in size (as said) they can be different materials. exhaust valves are usually non magnetic..  so you can use 2 exhaust valves but not 2 inlets

Another problem that would show similar symptoms is a worn cam follower or cam ? (presuming the rocker pivot is not worn?)

To remove the valves I use a deep socket, stuff the combustion chamber with some rag, place the head face down, a good whack on the socket when placed on top of the spring cap will release the collets... Keep a firm grip on the socket or the collets will fly off never to be seen again 

John

In my earlier picture, the intake valve is to the right.
In the pictures below you'll see that the top of the valve stem on the intake valve is actually closer to the top of the spring collar then is the exhaust's top of valve stem.
Yet, the overall height of the exhaust valve assembly is higher as shown in the original pictures I posted demonstrating the difference with the level.
At this point in time I'm suspecting an incorrect replacement valve has been installed  - one with at least a shorter stem.

Ray - you have a way of explaining the valve removal by socket & impact that makes it seem less severe.  At this point there's nothing to be gained that I can't wait to execute tonight or tomorrow.  The valve spring compressor is supposed to be delivered today.

I located an Intake valve that's for sale here in the US, but I'm a bit concerned about the surface degradation.  I've attached a picture for reference.
Does anyone have thoughts on whether I should be concerned about this and move on or simply just knock the crud off it and call it a day?

that valve looks fine to me - put it in your battery drill and hold some fine wet & dry or emery cloth on it to polish it up



ian