your leaking somewhere. As others have said up to 14v is what your looking for. Anything less than 12v indicates a duff battery I think. Soldering as you have done is a sure way to get a good connection as I find bullet connections, especially when wet will partially fail. Soldering rectifies this. Only a small amount of corrosion will effect an earth connection. I had exactly the same problem with an old VW camper which seem to be wired in a similar way to British bikes. It turned out to be corrosion on the earth and when I found and corrected it, everything worked fine.

interesting. So in the end it was a timing issue? I found with my M21 that using the timing hole in the top of the cylinder head with an old wheel spoke with TDC marked along with a mark just before to set the contact breaker to just opening worked well. It used to need retard to start but for the last year or so this wasn't necessary. Not sure why it would change unless the timing had slipped. On checking it was perfectly set. I did, however, put on a new carb which was the 276 with separate float. Now it suffers from fuel starvation!! When it's runing it is fine and dandy. I had the magneto rewound and set up but still find hot starting a problem. Wait 10 minutes and it's fine. I am interested to know how you set the timing?

I read somewhere about boiling in a solution of water with bicarbonate of soda. I did this and completely ruined the carb as when I dried it out and blew air through the tubes, it seemed to get filled with some sort of jelly!! I made a right pigs ear of the job, so I bought a new carb from Amal, a 276 to fit the older iron head and this solved the fuel starvation problem but it's an expensive way to solve a simple problem. Other suggestions in this thread are a better bet so whatever you do, DON'T use bicarb. Also when tightening the bolts NEVER over tighten. I think the torque is 4lbs per square inch so this is not much more than finger tight. That was another mistake i made and the carb bit where the 2 nuts fit onto the barrel warped.

I got one of those gadgets to put on the oil pipe to stop wet sumping. Which pipe does it go on the outer or inner?

that solves my problem as i was thinking the manual saying that they should be 18/20 psi was low. Must have been running
round with the tyres too low for some time! I shall pump them up.

I have a notion that upgrading the carboretter on my M21 to concentric from the 376 mono block may be a good step. I figured it would fit closer to the inlet due to the float chamber being underneath, this the dynamo went get in the way and I am informed the bike should run more evenly. Could anyone please recommend a suitable concentric carb for the M21?

thanks for the advice. In short, 0nly a madman would venture out around Benson at minus 8. I have come off in black ice
before years ago and i remember as i was falling off thinking, wow that was interesting, there was nothing I could have done
to avoid it, except stay in bed.