2012 FLHTK 44k miles, Stage I Air Filter, SE Exhaust, V&H Power header, ECM was flashed by HD 5 years ago when mufflers, headers and air filter were installed. Bike runs fine no issues. New spark plugs, gaped properly, good fuel.. But after a ride, then stop to get gas or eat and come back out to start bike, turns over a little more than normal then bam a loud backfire through the exhaust, then the bike starts. Does not do this every time. Bike is not throwing any codes. Have read that a faulty eng temp sensor may not throw a code and can cause the ECM to think the temp is a much colder temp, causing a cold start thus dumping more fuel than needed. Thanks for any help on this one..

 

With all the folks packin' these days, this end badly. Somebody help this poor devil...

 

Is it backfire or the compression release? I have found, especially when hot, I don't wait for the fuel pump to stop when first turning on the run switch. Meaning, as soon as you hit the run switch, hit the start switch. My bike usually starts in a second or two....no compression release sound/backfire.

 

My compensator was going bad when this happened tome.

 

Thanks. Its in the muffler.

 

Do you use the kill switch to turn it off?

 

Ignition switch..... I've ran the wiring diagram down on this one. Some say it matters, but technically both do the same thing on the same circuit.

 

Have you ever run fuel injector cleaner through it? I wonder if an injector may be weeping and letting raw gas accumulate during shutdown.

 

I've had that happen when letting go of the start switch too soon. It hit a time or tow but wasn't really started, let go and bang! Then starts right up when I try again.

If that's your case, just be very mindful of firmly holding the start button down until you know for sure it started.

Good luck!

 

So this is the kind of the same thing as cutting the bike off with the kill switch in a hurry. The engine cycles with the spark missing and air/fuel mix ends up going through the engine and into the exhaust. When the bike fires up, the excess mixture fires up and bang. Can also happen if the timing is off (too rich).