Cylinder is not firing on a road king - FLHRCI Road King Classic Harley Davidson Motorcycles

check compression in front and rear cylinder

A spark plug may fire when out of the cylinder, but not fire properly when under compression. Replace the plugs and get your coils checked out for correct resistance and operation. You will find the correct readings in your manual.

Perform a compression test on both cylinders. If there is a significant difference between the two you may have a stuck ring or stuck valve from sitting.

Could be. Check for DTCs first.

Backfiring out of the exhaust is usually an ignition problem. Unburned fuel is getting into the exhaust system because it's not being ignited in the cylinder. When the engine fires on that cylinder again, it ignites the raw fuel in the exhaust causing the pop that people call a backfire. I'd investigate the ignition system. Connect a timing light to each of the spark plug wires if it has a single fire ignition or either of them if the ignition system is the stock dual fire. Start the engine and watch the timing light to tell if the engine is missing as the light will miss a flash.

Good Luck
Steve

Check the pipe right where they come out of the heads. It depends on what type of exhaust system you have on your Road King. If the stock exhaust is on the bike, the rear cylinder exhaust is directed to both mufflers. With the exhaust from the front and part of the exhaust from the rear cylinders going to the right side muffler, it gets more exhaust than the left side and runs hotter. Like I said, check the temp of the exhaust pipes at the cylinder heads. If one of them is cold, that cylinder is not firing. As long as both of the pipes are hot there, you're fine. Just ride the bike and have fun.

Ride Safe.
Stevev

What are the DTcs??


disconnect the fuel injectors to see it this stops the code from setting


Test the coil

By design, as engine gets "too" hot idle goes down and firing of rear cylinder is skipped every second or third cycle.