Spark plug wires connected in wrong order?
Timimg chain jumped a tooth?
Bad intake valve?
Worn out camshaft lobe(s)?
Bad/wet distributor cap?
Faulty accelerator pump in carb? A LEAN MIXTURE WILL CAUSE INTAKE POPS ALSO A BIG VACUUM LEAK CYLINDER WILL PULL IN STRAIGHT AIR WITH NO FUEL MIXTuRE a dirty coil tower allowing spark to jump under load also a oil fouled spark plug or a closed gap or cracked plug check all wire end make sure non have corrosion including coil wire both ends make sure the metal end are clicking into dist cap terminals then slide rubber boot doen over cap make sur netal plug wire ends clic on spark plugs then slide boot over plug
AnswerSounds to me that your vehicle is off time. Check the timing on it. If the timing is off it will backfire through the carb and also if it is cross wired (firing order wrong) it will backfire through the carb.
probably 180 deg out on timing
Spark plug wires incorrectly connected or it is way out of time.
Too much fuel pressure. that typically happens when needle valve (carb pressure control) is blown off the seat.
Yep.
you can check the catalytic converter it may be plugged and cause it to backfire through the carb
A fire in the carb.
As with any engine, timing, and also carb problems.
Yes it would.
u have an intake valve bent or sticking open. run a compression check with all the plugs out and butterfly to carb open.
yes, backfiring is always due to ignition or timing problems. Backfiring through the carb can be a symptom of a lean condition.
running lean can cause your 400ex to backfire ..if it backfires on deceleration its lean ...if it pops on acceleration its running rich.====carb issues