Stalling and backfireing

Some common causes and potential solutions:

Air/Vacuum Leak: If your Harley develops a vacuum leak in its air intake system, the air-fuel mixture becomes too rich. This can cause frequent stall outs, especially after the bike warms up. Vacuum leaks often occur due to dried-out or cracked air intake boots, faulty gaskets, or worn-out carburetor seals. When air escapes from the intake system, the fuel fills the empty space in the combustion chamber, altering the air/fuel ratio and negatively impacting combustion. Severe vacuum leaks can lead to excess fuel flowing into the exhaust system, causing backfiring and stalling while riding.

Clogged Fuel Tank Filter/Fuel Injectors: A blocked fuel tank filter (due to coagulated fuel, moisture, dirt, or corrosion) impairs fuel flow, resulting in a lean air/fuel ratio. On fuel-injected Harleys, clogged fuel injectors produce similar symptoms. Regular maintenance, including cleaning and inspecting fuel filters, helps prevent these issues.

Faulty Cam Chain Tensioner: A malfunctioning cam chain tensioner can affect engine timing and cause stalling. Regular checks and replacements are essential to avoid this problem.
Faulty Cam Position Sensor: The cam position sensor plays a crucial role in ignition timing. If it malfunctions, it can lead to stalling and backfiring.

Clogged Air Cleaner: A dirty air cleaner restricts airflow, affecting combustion efficiency. Regularly clean or replace the air filter to prevent this issue.

Ignition System Failure: Faulty ignition components (such as spark plugs, ignition coils, or wires) can cause misfires, backfires, and stalling. Inspect and maintain these parts regularly.

Compromised Battery Terminal Connection: Poor battery connections can disrupt electrical flow, affecting the ignition system. Ensure clean and secure battery terminals.
Remember that diagnosing and addressing these issues may require professional assistance. Regular maintenance and timely repairs can keep your Fat Boy running smoothly on the road.

code p 0300 is random misfires ==causes --low fuel pressure , problem/dirty injectors , plugs , ht leads , ECM vacuum leaks

It could be a dirty idle air control valve located on the throttle body but when you said it backfires after running a while and before stalling, this sounds like a clogged catalytic converter. When blocked they will cause the exhaust manifold to glow red igniting gasses on the exhaust stroke, backfiring. A clogged cat will result in a loss of power as if you are trying to pull a trailer full of rocks uphill.

If you can find the PCV valve and it's associated plumbing, I promise that you'll find one of the rubber elbows that connects it to the intake manifold has rotted out and is leaking vacuum. This is a very common problem.

Sounds like a combination of things. First, are you using high octane fuel? If not, try a couple of tank fulls of that. You mentioned "Power Knocks" when starting off from a complete stop. This is typical of detonation due to low quality fuel.

As for the backfiring and stalling. The engine should idle at about 1000 RPM or so. If it's idled lower thant this, stalling is a possiblity not to mention poor oil of the bottom end. The backfiring could be caused by an air leak into the exhaust system. The mixture in your exhaust system should be overly rich for combustion when you backing down using the engine. If the system is sucking air in at a joint sometwhere, it leans the mixture into a combustable mixture and it ignites causing the back fire. If you've removed the "anti-tamper plug" giving you access to the idle mixture screw, back it out about a half turn and see if that helps.

Good Luck
Steve

most likely the feul pump. test the feul pressure with a gauge. look of ther little metal feul line on the intale manifold. tst pressure. have freind listen at the rear of the truck for the pump prime. key on only. then start the truck, friend should hear pump running. could also need a timming chain but pump is more tlikely

Hello, it sounds like the timing belt may have slipped on the gears, the top part of the timing cover can be removed to check the timing marks with the engine at TDC.

check the mass air flow sensor in the air cleaner tube,it may have a white piece of fuzz on it from the filter and it changes the readings of how much air its getting.

engine backfires, can be in egr system, vacuum leak,damaged valve springs or sticking valves, intake air(vacuum) leak. any of these problem could make engine stall!!