Backfire or Afterfire on 200x -- cause for concern?

[Trimoto Mike]

On one of my ATC 200x trikes when I let off the throttle it always pops and keeps doing it. Yesterday on an extended run - about 13 miles - it would also do this but I could hear knocking (burbling sounds) at partial throttle and then the backfire when I let off the throttle.

Is this really bad for the bike? The exhaust is pretty open with an aftermarket exhaust -- no baffles at all, so no back pressure. This bike has lots of power and torque -- more than my other over-bored 200x.

[shortline10]

A leak at the exhaust head pipe or a lean idle jet are the usual cause from deacceleration backfiring .
Try opening up the air fuel screw one turn to see if it gets better .

[Trimoto Mike]

A leak at the exhaust head pipe or a lean idle jet are the usual cause from deacceleration backfiring .
Try opening up the air fuel screw one turn to see if it gets better .

Sorry for ignorance, but my carb has an idle screw and a pilot screw. Should I adjust the pilot screw?

[El Camexican]

Sorry for ignorance, but my carb has an idle screw and a pilot screw. Should I adjust the pilot screw?

The rule of thumb is that if your screw is located between the center of your carb and the air filter it’s an air screw you’d turn it inwards to riches the pilot circuit. If the screw is located between the engine and the center of the carb it’s a fuel adjustment screw and you turn it outwards to richen the circuit.

Usually 2 strokes come with air screws and 4 strokes come with fuel screws.

Follows shortline’s advice and if opening the fuel screw doesn’t help you could have a dirty pilot jet, or another problem like the leak he mentioned or possibly your exhaust valve clearance is too tight.

[Tri-Z 250]

Popping off a hard stab/run indicates a lean spot on top usually. Test it by taking the air box cover off...it should get worse. The bottom flow jet doesn’t do it within a 1/4 to 1/2 turn; consider dropping the needle clip one spot to richen the flow across the entire carb. Put flow back to its 2-2-1/4 turns out.

Take a wooden dowl rod and place it to the cam chain side. Place one end to motor cover the other with your hand slightly, place your ear to your hand. While at idle listen for that gurgle(cover other outer ear). Could be chainslap?
Any rubbing or loud mess grind at idle or especially after a quick rev: your guides and chain are at fail point.

[Dirtcrasher]

Sometimes turning the pilot out 1/4 to 1/4 turn eliminates deceleration popping/backfiring...