1971 BMW 2002 not idling and backfire

I'M NOT A BMW KINDA FELLER

I DO KNOW CARBS AND TIMNG

IF THIS WAS A "SUDDEN OCCURRENCE" KINDA THING

INVESTIGATE THE INSIDE OF THE DISTRIBUTOR

INSIDE THERE, THERE ARE "WEIGHTS THAT SLING OUTWARD" AS ENGINE RPM INCREASE (THIS IS DUE TO CENTRIFUGAL FORCE)

THE POSITION OF THESE WEIGHTS SORTA MOVE THE TIMING TO COMPENSATE FOR THE ENGINE SPEED (THROWS THE SPARK SOONER AND SOONER) THIS "ADVANCE" KEEPS THE SPARK HITTING AT THE CORRECT TIME (WE CAN SPEED UP THE ENGINE- BUT WE CANNOT SPEED UP ELECTRICITY- THUS THE NEED TO SEND THE SPARK SOONER)

WELL ANYWAY- THE WEIGHTS ARE RETRACTED AS THE ENGINE SPEED DECREASES

USING A SPRING(S)

IF THE SPRING BREAKS OR COMES LOOSE, THE WEIGHT STAY "THROWN OUT" AND THE TIMING IS ALWAYS ADVANCED

THE FIX HERE IS REPLACE THE SPRING WITH A CORRECT ONE OR JUST REPLACE THE DISTRIBUTOR

I'VE SEEN THIS MANY TIMES WITH MY/ AND OTHER VEHICLES

IF THIS IS NOT YOUR CASE,

HAVE YOU MOVED THE TIMING?

MAYBE ACCIDENTALLY MOVED/ SWAPPED A SPARK PLUG WIRE TO ANOTHER POSITION?

SOMETIMES A VACUUM LEAK CAN CAUSE SIMILAR ISSUES - IT MAY EVEN BECOME WORSE AS YOU MONKEY WITH THE TIMING OR CARB SETTINGS IN AN ATTEMPT TO COMPENSATE FOR THE "MYSTERIOUS/ GHOST/ UNKNOWN VACUUM LEAK. WHEN IT IS FINALLY FOUND, YOU MUST "UNDO" WHAT YOU DID!

KEEP US POSTED

THE MEDIC

Thanks a lot. I will check it up. Carb was rebuild now distributor could be the problem. It is 43 years old. Thanks again