Advance angle on a C15

[Barnsey]

My No 1 bike, C15, is still not starting, with the new rectifier, despite having a good current of 2.6A.

I have stripped down the distributor, and it is stamped to show that it has an advance of 12 degrees.
Is that right? I thought it was 10 degree on early bikes like my 1962 model.

 What effect would it have?     

[limeyrob]

Not much, is that the advance at the unit which would be 24 deg on the timing? I suspect so.  Even then this is only 4 deg difference.  Since the timing is set for full advance and that number is the amount it retards it should make no difference to the running and may make starting a bit easier.

[Barnsey]

Okay.  I stripped, cleaned and reassembled the distributor, and now it is back on the bike with the timing set. 

I am concerned about the compression.  I measured it at around 60 - 75 psi.  No 2 bike, which runs, shows 90 - 110 psi, and, according to an online search, it should be 110 to 140.

 Would this stop it from starting?  Maybe, but I imagine I would be hearing a pop at least. 

[limeyrob]

Is that 60-75 kicking with the throttle wide open?  That's very low and it may not start.
Have you tried putting some thick oil down the plug, this will seal the piston for a few kicks and show it its the rings.
Are the tappets set correctly so the valves close?

[Barnsey]

We managed to get it started, in the end, by setting the plug gap. 

I have some classic car oil to put in (20/50?), so I'll do that next. And, I'll oil the bores as you say. 
I am sure it still has 10/40 in it, as that is all I had at the time I was putting it back together. (It seems like a long time ago).

[rhyatt]

Any oil squirted into the bore via the plug hole will momentarily  seal the rings if they were the culprit.
Always hold the throttle wide open when doing a compression  test.
As already said,  check the valves
I've you get an increase in compression  psi with the oil , then the rings/bore may need attention
If there is no improvement  with the oil, then the compression  is creeping  past the valve seats and a regrind will sort that

[Barnsey]

I squirted some oil into the bore and the compression raised from 75 up to about 90psi

[limeyrob]

OK at the very least it needs rings.