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i have 2 mowers with identical briggs 6.5 hp engines- both model 123K02. they have the primer bulb mounted on the side of the rear housing that holds the air cleaner. one primer bulb has a hole in the middle, the other does not. is this how the float bowl vents? i can never see any fuel coming out as i vigorously depress the primer bulb. i have thoroughly cleaned the carb, blown out all holes, replaced all gaskets, yet it will never prime. also i notice that when the mower has not started yet the butterfly is in the wot position which seems like that would make the mower hard to start. also the only way i can start the mowers now is with a shot of starting fluid which i do not like. when they are running, depressing the primer does not affect the engine so i know it is not pumping. how does this system work?---very frustrated- thank you

Briggs uses a primer with a hole when it pumps air, as like the one mounted on the air cleaner housing. the no hole primer is used when the primer is part of the carb itself. Yes the carb bowl vents through the primer hole on the engines with the primer mounted on the air cleaner.

It is very common for the air cleaner backing plate, to warp were it mounts to the carb, and if it doesn't seal, when not prime. the fix is to double gasket the air cleaner backing plate to the carb.

ILENGINE said:

Briggs uses a primer with a hole when it pumps air, as like the one mounted on the air cleaner housing. the no hole primer is used when the primer is part of the carb itself. Yes the carb bowl vents through the primer hole on the engines with the primer mounted on the air cleaner.

It is very common for the air cleaner backing plate, to warp were it mounts to the carb, and if it doesn't seal, when not prime. the fix is to double gasket the air cleaner backing plate to the carb.

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when working properly- should i see i spray or a dribbling of fuel from the emulsion tube? also is that normal that the carb is in wot position during starting position?

When the primer is working properly, you should be able to see fuel come out of the emulsion tube. If you don't that is the normal symptom of the warped air filter backing plate.

the governor spring will hold the throttle WOT when the engine isn't running.