Small Engines (Lawn Mowers, etc.): Engine wont run unless chocked, spark plug wires, partial obstruction

Question
I have a Briggs 42a707 that won't run smooth unless 1/2 to 3/4 choked. Less than that runs very uneven and almost stalls, no power. thanks for your help

Answer
Ron,

There are one of two things going on here.... Either the carb, fuel line or fuel filter has a partial obstruction and when you choke it you compensating for it,  OR

It is only firing on one cylinder.

With the engine stopped, remove one of the spark plug wires and start your engine.  If it starts, shut it off, Put the plug wire back on and remove the other one.  If it starts its a carb problem, if it doesn't start with one of the plug wire removed you have a bad cylinder.  This could be a broken con rod or bad ignition.

Typically the symptoms for this type of failure is the engine will start and run fine until you engage the blades.  Then it will die.

Let me know what you find!