If swapping the ignition leads and plugs doesn't cure the problem, would go back to the carbs .
I had an exasperating time getting my '81 R65 to run, the left cylinder wouldn't run no matter what I did .
I finally found the problem after spending way too much time troubleshooting the problem .
The idle jet was clogged, what I didn't realize, when I was cleaning the carb parts, is the idle jet has two holes drill in it, when I sprayed carb cleaner in it, the cleaner came out the holes in the sides of the jet body, not out the hole at the end , that meters the fuel .
Hope it's a quick fix for you !!!!!