have an assistant crank the engine with the dizzy cap off or turn the engine by hand with the car in gear and check if the points are arcing! I've changed 5 condensers the past week dont take them for granted. I had to switch to a genuine lucas to settle the problem out.. 

So I took the mini out for a drive last weekend...65 Cooper S, dual HS4, maticulously maintained and tuned and always runs like a top....Started the drive out as normal and about 10 mins in on an easy drive it felt like I lost cylinder(s)....Limped home....The first test was to see if I lost spark...Changed all plugs, no help...all of the old plugs looked normal, no wet plugs, etc...checked points and spark appeared on weak side at points....Changed condeser and spark at points appears strong....then check spark at each plug and they are very strong...shocked the piss out myself a few times....Car will idle but very rough....If i pull either plug wire 3 or 4 the car dies....if I pull wire 1 or 2 the car still runs on but a little rougher....the oil reserves in the carbs appear good and the sliders appear to move up and drop normal...I do notice that the carb for 1&2 is blowing back fumes when you blip the throttle....All carb linkage is tight so nothing appears out of wack...The motor oil is clean as a whistle and I am not getting any unusual exhaust smoke or blowby???  I feel like something went wrong with the carb for cylinders 1&2...almost like fuel starvation in the cylinder 1&2...I pulled the fuel line to 1&2 and the pump is pushing fuel to the bowl....The car has been driven minimal over the summer months due to AZ heat but I start it once very 2-3 weeks....

Any thoughts even if it is a stab in the dark???