From experience, a quick sniff of the exhaust when the no start occurs….
>If the exhaust while cranking smells of raw fuel it’s it’s an ignition problem
>If it doesn’t smell of raw fuel it’s fuel delivery problem.
��SPARK
I would check for spark quality ….AT the spark plugs!….engine cold. Compare that to the spark quality when the no start condition is active.
All good…same spark quality. Move on.
Weak spark work back upstream. Or go to the coil and check spark quality there. Good at coil look to cap , rotor, coil wire…then ignition wires to plugs.
⛽️FUEL compare the accelerator pump discharge cold engine to no start condition.
If it’s weak or absent with a FEW full pulls on the throttle during no start condition. Remove fuel line at carb and crank engine, discharge ~ a pint into a glass jar. If no discharge work back from there to the tank. Let jar sit and see if it separates…water at the bottom….fuel quantity, quality and contamination check, sniff it smells “stale”. An Aquired smell to recognize, but “not normal “ .
Meanwhile if Fuel to the carb, but accelerator pump discharge runs out after a few full pulls on the throttle or weak and runs out of shot after a pull or two ….Fuel inlet needle and seat problem.
A logical check of fuel and ignition systems will yield a first time, viable repair. The repair is the easy part, a proper diagnosis makes that possible.
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