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Sometimes the backfire can be from unburned fuel in the muffler too. If you shut off the old engines at WOT or higher RPM's, they spark goes away but the fuel keeps being dragged into the cylinder, and, unburned out through the exhaust. So in essence, you have fuel vapors in the muffler.


What causes a 1973 Pontiac 350 engine to backfire through the exhaust? A large backfire is most likely caused by a bad spark plug or plug wire. Unburned air and fuel pumped into the exhaust will ...


Model 858F8A, the motor is backfiring and stopping the engine dead every five or ten seconds. The backfire is coming out the exhaust, not the carbs. Checked spark on all three with spark checker, all are firing strongly. Pulled wire from each plug one by one, grounded that coil wire to the spark tester, and ran.


Backfiring through the muffler or carb? Makes a difference as to how to proceed. I’m thinking valves not closing properly or carb running rich. When you post back include the model and spec numbers, I’m think either an HH80 or HM80 engine. Waiting to hear back.


Briggs and stratton then replaced the engine after two years of fighting with them and more than $1000.00 spent on their part. The new engine has only 5 hours on it and is now backfiring thru the exhaust, but has not spewed gas out of the carb as of yet. Contact the U.S. Consumer Protection Commission in Washington and report this to them.


A backfire is combustion or an explosion produced by a running internal combustion engine that occurs in the exhaust system, rather than inside the combustion chamber.Unburnt fuel that is ignited in the exhaust system can produce loud sounds even if flames are not present at the tailpipe, which is called an afterburn or backfire since a backfire occurs in the exhaust system.


4: Backfires in Exhaust Note: It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.


The engine backfire through the exhaust ONLY and not all the time either ! Backfire through the driver side on the number 5-6-7-8 cylinders. A hot muffler and gasoline with a high alcohol content may cause the engine to backfire, also. When the air/fuel ratio is excessively lean (not enough fuel), the engine may backfire through the intake ...


Backfire in engines is caused by simple chemical malfunctions that can be easily rectified. A backfire in a lawnmower engine can damage both the engine and the exhaust as burning fuel explodes. Take care to avoid close proximity to a backfire and the motor until you've determined the cause and fixed the problem.


Is it backfiring through the intake manifold or an afterfire through the exhaust. Since you replaced plugs and wires and distributor parts are you sure you replaced them correctly to the proper cylinder? Is there a chance you moved the distributor slightly, could affect the timing. Hopefully you do not have a bent valve.