OK. So I have now put the carb back to 1600GT jetting. Ignition timing checked as 9 degrees BTDC at 800rpm. Idle adjusting screw 1 1/2 turns out.
The first run started out ok but I noticed that the exhaust was popping slightly on overrun. This got worse as time went on. Otherwise engine running well (and seemed better than with the original jetting) . A few miles on and the engine was getting lumpy at low revs and stalling when the car was stopped. I eventually pulled in to a car park to check things out and let things cool down. I had to back out the idle adjusting screw about another 1/2 turn to get the engine to run smoothly. Managed the 3 miles back home ok. I checked the timing which was unchanged. I noticed not much fuel in the fuel filter which had some debris in it (I'll change it out) but that would not have changed overnight. There didn't appear to be a vacuum in the tank when I took the fuel cap off so I'm happy that it's ventin ok.
I'm a bit concerned about what causes the "popping" from the exhaust. I thought it was incorrect ignition timing. Any suggestions other than "rolling road"?
