not a cossie problem but on a N/A 4cyl mini engine, bizarre till we worked it out anyway.

with distributor / coil ignition, starts running on 3 cylinders (felt like a plug lead had fallen off). to try and indentify the faulty cylinder (or plug) we take each lead off in turn.

the engine is idling at the time.

removing #1 causes the engine to slow till almost stalled.
removing #2 increases engine speed.
removing #3 has no effect on engine speed.
removing #4 has no effect on engine speed.

answer later.....