While driving home from work this evening the engine started shaking and popping badly and had little power, engine was cold with little choke. It sounded like something serious was wrong popping and snapping like it was badly misfiring or runnig on 2 or 3 cylinders. Shortly after the throttle cable snapped. I managed to get home running on full choke. The engine had a very rough and uneven idle. I fixed the throttle cable temporarly and took the car out for a drive. It was driving terrible snapping and popping. It ran clean at full throttle but no power. Then suddenly after 2km it started to run fine, no popping or snapping, idles ok. What can this be? I've just replaced the carb and it's probably running a little rich because the carb came from a B21A, I have B19A. Black smoke from exhaust when revving in neutral. Could it be that the plugs have been fouled by an overly rich condition? I plan on changing the needle in the carb. I also noticed when installing carb that the hole the needle valve goes in is oval, not round so i will change that too. Do i need a special tool for this?