Seems to be a fuel problem, fuel not getting thru to cylinders but runs on easy-start (did this to eliminate poss. electrics problem) fuel tank full and switched on !!!

More and better information will help you get quicker and better answers. I will assume you are asking about a JD LA120 or D120 or L120 or perhaps even an X120. However, these models do not have fuel injectors.

Many things to consider but, let's try the simple things. You didn't say, so I am going to assume the mower is at least newish, not 30 years old. Let's say you have less than 300 hours on the engine. Let's further assume it worked last summer, or last week, but now it's acting up. Let's also verify the battery is in good shape and fully charged.

A mechanically functional (meaning all the internal parts are working, i.e. pistons, valves, etc) engine requires 3 things, air, fuel, spark. So the quickest way to start your diagnostics is to remove the cover over the air filter and then remove the air filter. I do not recommend spraying Quick Start.

1. remove air filter
2. put throttle on fast run (do not choke)
3. pour an ounce or two of fresh gas into the carburetor
4. crank engine (15 to 20 seconds, rest to cool the starter, repeat 3 times if it does not fire at first).

Removing the air filter and placing the throttle at full speed, no choke, eliminates the "air" question. Dumping in the fuel eliminated all fuel related questions. What's left? Spark. If the engine fires and runs a bit, then dies, you have eliminated the spark question. The engine started so Spark and Air are good; you have to track down a fuel problem.

If the engine does not fire, you have eliminated the Air & Fuel questions; you must tract down a Spark problem.

Tracking down fuel problems.

1. Make sure there is plenty of fresh fuel in tank.
2. Remove fuel line from filter and remove the filter, gas should pour out of the hose coming from the tank. If it does not, remove gas tank cap. If fuel flows now, you need to unclog the cap vent or replace the cap. If the fuel still does not flow then blow air from the filter end of the hose back up through fuel line to blow out blockage inside the gas tank. Once you have fuel flowing out the line to the filter, PUT ON A FRESH FILTER. Try cranking the engine. If it still does not start move on to the carburetor.
3. Note: many systems have a fuel shut off solenoid. This is a small black cylinder on the bottom of the carburetor. It has two wires running to it. It should make an audible click when you turn the key on.
4. NOTE: if battery voltage drops below 9 volts when cranking or while the engine is running, the fuel solenoid will not function. That means the engine will not start or will die soon after starting. So check your battery voltage before, during, and after cranking. If the battery voltage is good before but drops below 9 volts while cranking this is generally a sign the battery has one or more bad cells. Replace the battery. If the battery is in fact good and the voltage is still dropping you may have a bad starter motor and it is drawing to much amperage.
5. Ck to see that the carburetor bowl is full of fuel, if not...you may have to remove, disassemble and clean the carb at this point.

Tracking down Spark problems.

1. verify battery fully charged.
2. verify the fuel cutoff solenoid clicks when you turn the key switch
3. get fresh spark plugs and verify gap
4. install plugs and crank.Perhaps verify spark with a spark testor

If these simple steps do not solve the spark problem, you have a Spark problem that moves into the arena of complex. You will need to check coil gap and coil performance. If it still doesn't start you will need to diagnose the electrical system for wiring and safety switch problems, key switch problems, fuses, etc.

Once you get it running be sure to replace the Air Filter with a new one.

These simple steps solve most starting and running questions and problems.

Check for good , strong spark. Take spark plug out and ground the outer core of the plug to the engine. Hold the plug with a pair of insulated pliers. Have someone crank the engine while you observe for a good strong blue spark. If the spark looks nice and bluish, then next would be to clean the carburetor. I suggest trying a "quick clean before taking the carburetor bowl off. Take spray carburetor cleaner and spray inside the carb throat with the air cleaner off. Also take about 1/2 can/bottle of fuel line injection cleaner and put it in the gas tank. Then try starting the mower. May sure the gas in the tank is fresh.

saws use a flow thru carburetor design , fuel is drawn out of tank and excess unused fuel is returned to tank thru other line , the clear primer bulb starts this "flow thru " process and engine vacuum (running ) continues it

when replacing lines many folks forget what line went thru what hole (change them one at a time ) this requires a little detective work to figure out what hose thru what hole goes , with a little fuel in tank tilt saw front to back , see what hose always gets the end covered up with liquid level , this line always goes to farthest hole in tank back and that hose goes to fitting nearest the primer bulb ,, due to process of elimination there's only one other possible place for the other line

Many things to consider but, let's try the simple things. You didn't say, so I am going to assume the mower is at least newish, not 30 years old. Let's say you have less than 300 hours on the engine. Let's further assume it worked last summer, or last week, but now it's acting up. Let's also verify the battery is in good shape and fully charged.

A mechanically functional (meaning all the internal parts are working, i.e. pistons, valves, etc) engine requires 3 things, air, fuel, spark. So the quickest way to start your diagnostics is to remove the cover over the air filter and then remove the air filter. I do not recommend spraying Quick Start.

1. remove air filter
2. put throttle on fast run (do not choke)
3. pour an ounce or two of fresh gas into the carburetor
4. crank engine (15 to 20 seconds, rest to cool the starter, repeat 3 times if it does not fire at first).

Removing the air filter and placing the throttle at full speed, no choke, eliminates the "air" question. Dumping in the fuel eliminated all fuel related questions. What's left? Spark. If the engine fires and runs a bit, then dies, you have eliminated the spark question. The engine started so Spark and Air are good; you have to track down a fuel problem.

If the engine does not fire, you have eliminated the Air & Fuel questions; you must tract down a Spark problem.

Tracking down fuel problems.

1. Make sure there is plenty of fresh fuel in tank.
2. Remove fuel line from filter and remove the filter, gas should pour out of the hose coming from the tank. If it does not, remove gas tank cap. If fuel flows now, you need to unclog the cap vent or replace the cap. If the fuel still does not flow then blow air from the filter end of the hose back up through fuel line to blow out blockage inside the gas tank. Once you have fuel flowing out the line to the filter, PUT ON A FRESH FILTER. Try cranking the engine. If it still does not start move on to the carburetor.
3. Note: many systems have a fuel shut off solenoid. This is a small black cylinder on the bottom of the carburetor. It has two wires running to it. It should make an audible click when you turn the key on.
4. NOTE: if battery voltage drops below 9 volts when cranking or while the engine is running, the fuel solenoid will not function. That means the engine will not start or will die soon after starting. So check your battery voltage before, during, and after cranking. If the battery voltage is good before but drops below 9 volts while cranking this is generally a sign the battery has one or more bad cells. Replace the battery. If the battery is in fact good and the voltage is still dropping you may have a bad starter motor and it is drawing to much amperage.
5. Ck to see that the carburetor bowl is full of fuel, if not...you may have to disassemble and clean the carb at this point.

Tracking down Spark problems.

1. verify battery fully charged.
2. verify the fuel cutoff solenoid clicks when you turn the key switch
3. get fresh spark plugs and verify gap
4. install plugs and crank.Perhaps verify spark with a spark testor

If these simple steps do not solve the spark problem, you have a Spark problem that moves into the arena of complex. You will need to check coil gap and coil performance. If it still doesn't start you will need to diagnose the electrical system for wiring and safety switch problems, key switch problems, fuses, etc.

Once you get it running be sure to replace the Air Filter with a new one.

These simple steps solve most starting and running questions and problems.

Seems that you have covered all the bases. The problem that you describe could be related to fuel lock or restriction in the fuel delivery system. Easy to check. Remove the air filter and have carb cleaner ready. If you are near the gen when it begins to quit, spray just a little carb cleaner to see if engine tries to run. If engine begins to run or continues to run with carb cleaner, then suspect fuel delivery problem. If the engine seems to stop quicker with carb cleaner, suspect flooding caused by too much fuel pressure (fuel pushed past the needle due to pressure in the tank; open fuel cap and listen for air pressure release). Fuel delivery problems are caused by collapsed fuel line, restriction in the fuel cut-off valve, restriction at the fuel filter (use larger automotive type), negative pressure in tank caused by no vent at cap. Rare problem with fuel delivery is caused by sudden heat rise at the carb causing fuel to boil out of carb. This is caused by the engine running very hot, lack of air across cooling ribs caused by debris or fan missing blades. You can eliminate the complete fuel delivery system by mounting a small fuel tank on a stand and running fuel line directly to the carb for test. The tank needs to be higher than the carb so that you will have good gravity feed. Good luck

HI, YOU DONT SAY WHAT THE BIKE IS, HOWEVER USING A CAN AND A LENGTH OF RUBBER PIPE, FIT ONE END TO TAP AND THE OTHER IN THE CAN, TURN THE TAP TO ON POSITION AND ALOW THE FUELTO FLOW,CHECK FOR CONSTANT FLOW THIS WILL ELIMINATE THE FUEL FLOW RATE ON THE ON POSITION, AGAIN TRY IN RESERVE POSITION AND CHECK FLOW RATE , POSS REASONS COULD BE SEDIMENT OR CONTAMINATED FILTER IN THE TAP, OTHER WISE DO YOU HAVE A TANK BAG FITTED WHICH MAY BE RESTRICTING THE AIR INTO THE FUEL TANK THROUGH THE INTAKE, CHECK FOR RESTRICTIONS AROUND THE FUEL CAP, OR THE RUBBER PIPE WHICH ALOWES AIR INTO TANK(SOME MODELS). TRY THE ABOVE FLOW RATE WITH THE FUEL CAP CLOSED FIRST THEN WITH IT OPEN AND CHECK FOR A CHANGE, HOWEVER, YOU MAY HAVE A RESIDUE OF MUCK OR WATER INSIDE THE CARB/CARBS UNDO THE DRAIN SCREW ON THE FLOAT CHAMBER, THE LOWEST POINT ON THE CARB AND ALOW ALL THE FUEL INSIDE TO BE REMOVED, THIS OPERATION SHOULD BE CARIED OUT WITH THE FUEL TAP IN THE OFF POSITION, CATCH OLD FUEL, AND DISPOSE OF, PAUL

these engines have a computer control, it can be tested for any faults that have occurred, I would suggest you buy a bottle of LUCAS Brand injector cleaner, it is poss the injector are not spraying evenly due to nozzle clogging. LUCAS is the only product that I have found actually works, just add about 1/2 bottle to the tank, a couple of full tanks should help clean the intake parts, also check the air cleaner for being dirty.. other problems are engine wear, check and make sure you have good compression, I would guess this engine has at least 160 PSI, check the plug and make sure it is clean and the color is a tan, if it is black or sooty looking you have a rich run condition.

sounds like you sucked up dirt in the carb needs to be taken off and cleaned

If you have a compression gauge, check the compression. Anything under 90psi is too low.

Check your flywheel key. If it is broken the flywheel will move and not fire at the correct time.

Note: if it does not sputter with carb cleaner then it's not your carb.

Next:
Remove your exhaust manifold. Look into the cylinder with a flash light. You are looking for scratches. Anything larger then a light fingernail is definite proof you need a new cylinder/piston assy.

If it passes that test do the following:

Pour mixed fuel straight into your cylinder until 1/4 full. Slowly pull your saw over while looking into the cylinder. If you see bubbles after the ring/rings go by then you need a new cylinder/piston assy. On rare occasions if no scratches are present on the cylinder wall or piston, you may be able to change just the rings.

Some Poulans vent thru a fuel line going from the tank to the carburetor. Some vent thru the cap but eventually the duck bill valve starts leaking fuel. Then I suspect some people change that cap to one without a vent, which causes the problem you are describing.