I've got an 02 FLHRPI that I've changed the injectors, coils & wires; cleaned the throttle body. No codes but bike is backfiring out of the throttle body, stalling. Will only idle for about 30 seconds and then starts backfiring out of the intake and stalls.

Checked the gas line to the tank and cleaned IAC and map sensor and IAT.

Any ideas of what's going on or what else to look at would be greatly appreciated.

Terri

 

"The main reason engine backfires is because a valve is not closed when the spark plug fires. If it is an intake valve, it will backfire through the intake. If it is an exhaust valve, it will backfire through the tailpipe.

There can be several reasons for this. The valves are adjusted too tight. Valve stems can be slightly bent and not allowing free movement up and down. Or the ignition timing can be off. There can also be dirt and sludge buildup that is causing the valves to stick.

There can also be a problem with the emission control system. There is an anti-backfire valve that can cause the backfire if it is bad.

Backfire in an engine typically results from various malfunctions related to the air to fuel ratio. Usually, backfiring occurs in carbureted engines that are running lean where the air fuel mixture has insufficient fuel. ("Running lean" is typically a sign of mal-adjusted carburetors or fuel injection where there is not enough fuel for the amount of air).

Afterfire occurs in engines that have an emission system malfunction (air injection system diverter valve), exhaust leak or unburnt fuel in an exhaust system in which the catalytic converter (if any) has been removed. When a biker shifts up and lets off the throttle, the engine has a moment of running rich or with insufficient oxygen. This causes an incomplete burn which causes the fumes to explode in the exhaust system.

The leak itself is the most dangerous aspect. Without it, the mixture would cool enough not to explode. A fuel injected engine may backfire if an intake leak is present (causing the engine to run lean), or a fuel injection component such as an air-flow sensor is defective.

Please refer to the Tuning Manual for information about correcting a lean condition or let your mechanic take care this problem.... "

Source(s):

http://harley-davidson-accessories.blogs...

 

I find that a valve not being closed is the least likely but most serious scenario.

most common is lean fuel condition

next is ignition timing too advanced

then valve/ valve seat/ bent/ valve/ cam timing/ pushrods/ etc etc


suggest that you find a way to test fuel pressure and volume

next, the electronic ignition system is very senstive- if some one has pulled the plugs and cranked the motor to "test" the ignition system...this can blow the coil

mike

 

+1 on the fuel test and lean condition. Weren't the pre 08's famous for that plastic flex hose in the tank cracking with age?