My John Deere lawn more just started backfiring through the carburetor. It’s a 20004 L 1 20. What would the possible causes for the backfiring be. I have change the plugs air filter fuel filter and oil.
That is a pretty good list. I will start with the lean carb just because I am an optimistic sort. The valve train will be my next effort. I noticed that you did not include weak coils or spark. I believe other items all involve the engine to be removed and disassembled.
Thanks for your suggestions. I will let you know what I find.
#6
Boudreaux In Eunice La.
After the carb, start with the valves....... Pop the valve covers off and check your rods for a bent one, then while turning the engine over look at the rockers to see if the travel is the same........
After the carb, start with the valves....... Pop the valve covers off and check your rods for a bent one, then while turning the engine over look at the rockers to see if the travel is the same........
I could not find adjusting screws for the carburetor. I know some are not adjustable.
I went through and adjusted the valves to .004 and rechecked them.
I checked the spark and it looked blue and bright.
Started the engine and it still pops through the carburetor worse under load.
Do you know what the lift should be on the valves? The clearance to start with was from.015 to .030 so I would think the cam was good
I am doing a compression test next to see if I have a valve problem.
It will run with the left plug disconnected and will not start with the right plug disconnected.
I just experienced this with a ~14HP Briggs & Stratton engine. Every fourth or fifth compression stroke a loud bang and fire from the carburetor would occur. Decided to part out the engine and entire mower due to a list of other issues. However, during disassembly, I came across a completely sheared flywheel key (cut in two pieces) once removing the flywheel.
Some of those engines run a diode between the two coils to prevent phantom sparks.
So try the engine again with the kill wires removed from the coils
Running the mower for a few minutes wit the cover off while you are diagnosing the engine will not hurt it but don't go mowing with like that.
he carb solenoid should stop the engine but you might like to keep some insulated pliers handy to pull the spark lead or make up a pair of jumpers to ground the coils.
Lets add bad gasket on the intake side. One has to laugh sometimes. People think (wrongly) that changing the oil and spark plugs cures everything. it cures nothing actually.
#12
sgkent
under load makes me think mixture. When the mixture goes lean the fuel molecules are farther apart, taking much longer to burn. That allows any remaining mixture to burn into the intake cycle and it spits back into the carb. So mixture is the first thing I look at on a carbed engine - piece of dirt in a jet, weak fuel pump, even old gas. In addition to other causes listed before this reply. another cause can be a backed up catalytic converter if it has a cat. On engines with points sometimes we see a failed condenser.
