So far. after reading the post from magneto man I took his suggestion, removed the float chamber, polished up the float needle and put it back together. Now it will not start at all, hot or cold, so I suppose that is progress of a sort.... I was aware of the need to keep the float vertical, it always dies immediately on the side stand or even slightly leaned over, another reason for considering a different carburetor. I can see the level with the float cover removed, not sure what is supposed to be. It does not appear to leak if the fuel tap is open and the tickler is not touched. Tank is full, cap is vented. No problems getting gas to flow.
Re the magneto, it has a spark hot or cold. I opened up a spark plug about 3/16" it sparks when I kick it over with the plug removed.
Spark plugs I tried among others, new Champion N7YC, also NGK BPR7E and BP7E and some NGK platinum tipped. All the spark plugs except the Champions have resistors, other than Champion I can't find spark plugs that do not have resistors. Spark plug resistance checked with ohmeter.
The HT wire and cap do not have resistors, checked with ohmeter.
Since the no start at all I did a rough timing check, the points are opening at about TDC on the compression stroke, ignition retarded, so that is good.
Re my starting technique, since I played with the carburetor settings, I start with gas tap open, kick it a few times, close the choke, kick it a few more times, one stab at the tickler, a few more kicks, another stab and so on, until finally there is gas all over the place and still no start.
Pull the plug and it is still dry. Kicking it through with the compression release pulled in I will get the occasional gun shot bang as unburned mixture fires in the exhaust pipe. I also try various throttle openings, including WOT when I figure it should be flooded.
As far as my technique for starting singles goes, I also have a Yamaha 500 XT which also has magneto ignition, and a reputation for being a bitch to start when hot. I can usually fire it up with one kick when it is hot, two or three when cold. There is a muscle memory thing happening there I am not totally aware of. It did take time to learn how to start the Yamaha, and it was hard at first but I can't really say what I am doing differently other than following the owners manual technique exactly and not over using the enricher thingy.
I have been chasing the comet starting problem since I got the bike a couple of years ago. Along the way I found the cam and followers badly worn, and replaced them. Cam timing was set using a degree wheel, not the the marks on the timing gears. As I posted earlier, when it does run it runs very well.
https://www.youtube.com/watch?v=qAoWlDEmGo4
See for yourself,
Comet Running
(Corrected the link.
BigEd)
I am leaning towards magneto replacement-rebuilding, guy has a rebuilt one on ebay uk for sale, he also sells dresses and ladies shoes, not that there is anything wrong with that
I would be a lot more confident about mag replacement if the effing thing did not have any sparks, but I also get that any one who thinks they know how electricity works is delusional.