1973 Karmann Ghia 1600 cc engine

My TRIKE has a 1973 Karmann Ghia 1600 cc engine and just recently it started back firing, I have replace plugs, points, cap, wires and adjusted valves. If anyone can give me another suggestion please do so.

your carb

Yes, check the carb but make sure the exhaust doesn't leak. Is the engine missing if so then check or replace the carb. You can get a rebuilt one for under $100.

More info would help, what carb is it? 30 PICT or 34 PICT-3, and what distributor do you have? What RPM /throttle position is it backfiring? It's possible you have a clogged jet, loose intake boot, or a leaking vacuum line.