Dobeck performance posted this about the decel popping...
We get numerous inquiries about backfiring (popping) on deceleration (slowing
down). In order to have backfiring or popping on deceleration you must have three things present in the exhaust system: SPARK, FUEL, and AIR.
A properly tuned fuel injected Harley Davidson cannot backfire (pop) on
deceleration from red line to about 2800 RPM’s or (example:2nd gear) 30 MPH to 55 MPH. The reason is that when you shut the throttle down on deceleration the INJECTORS SHUT OFF in that RPM or MPH range which removes an essential part of the explosion. Spark, NO fuel, and air means….. no explosion. If your Harley Davidson is backfiring (popping) within that range of RPM or MPH it could be one of the following:
1. Your bike is not fully warmed up.
2. Malfunctioning cylinder head temperature sensor.
If your Harley Davidson is backfiring (popping) below that RPM or MPH it could be one or all of the following most common reasons:
1. Air being drawn in through the left hand exhaust pipe on touring models
(aftermarket, or modified stock). Which can easily be determined by plugging off left pipe and making a test run.
2. Leaking exhaust flange gasket or pipe connection.
3. Intake manifold leak.
The problem is AIR getting into the exhaust system. By adding more fuel you can see a reduction in backfiring (popping) but that isn’t fixing the problem and it usually results in drivability and/or mileage issues. It is always best to eliminate the cause (AIR) rather than changing the effect by adding more fuel.
We get numerous inquiries about backfiring (popping) on deceleration (slowing
down). In order to have backfiring or popping on deceleration you must have three things present in the exhaust system: SPARK, FUEL, and AIR.
A properly tuned fuel injected Harley Davidson cannot backfire (pop) on
deceleration from red line to about 2800 RPM’s or (example:2nd gear) 30 MPH to 55 MPH. The reason is that when you shut the throttle down on deceleration the INJECTORS SHUT OFF in that RPM or MPH range which removes an essential part of the explosion. Spark, NO fuel, and air means….. no explosion. If your Harley Davidson is backfiring (popping) within that range of RPM or MPH it could be one of the following:
1. Your bike is not fully warmed up.
2. Malfunctioning cylinder head temperature sensor.
If your Harley Davidson is backfiring (popping) below that RPM or MPH it could be one or all of the following most common reasons:
1. Air being drawn in through the left hand exhaust pipe on touring models
(aftermarket, or modified stock). Which can easily be determined by plugging off left pipe and making a test run.
2. Leaking exhaust flange gasket or pipe connection.
3. Intake manifold leak.
The problem is AIR getting into the exhaust system. By adding more fuel you can see a reduction in backfiring (popping) but that isn’t fixing the problem and it usually results in drivability and/or mileage issues. It is always best to eliminate the cause (AIR) rather than changing the effect by adding more fuel.
