Q: The motor is a 1.6L on petrol and gas. It won't start on gas. And when you try to start it on petrol, it has spark and fuel and when turning over it backfires through the carby. What do I need to do to solve this problem and get the motor running?
A: Your timing may be off. Probably like 180 degrees or so.
Either that or a dead cow is actually caught in your exhaust