2 stroke carburettor primer bulb question

I would expect something that is intended to prime when used to have some sort of one-way valve that allows suction from the tank but not pressure into the tank. The fact that yours is putting air into the tank indicates that the valve is either leaking or is stuck in the open position.

If you can locate where the valve is on the route from tank to the poppet, you will find what the problem is. However if the valve is a flap that is supposed to move but is stuck and you have punctured the flap with your pin, you probably won't be able to fix it now.

I must admit to questioning my sanity as to how these things work. There’s one obvious one-way valve that I think only directs fuel back to the tank. I rather suspect that it should be sucking up fuel through the other connection to the carb which must be blocked somehow. I think I’ve misunderstood the normal flow direct of fuel through it.

Tim

Never use a pin or compressed air, just carb cleaner.

The bulb is a purge pump; it pulls fuel through the carb from the tank (via a drilling beside the check valve usually) and dumps it back into the tank. This means the carburetor is full of fuel before you pull start, so it doesn't rely on the induction pulses to prime the carb. Hence less pulls necessary.

Thank you. That's another unknown unknown ticked-off.

I worked this out once I got the new carb. ;-)

I dare the that the old carb could have been resurrected with some serious cleaning but with the low cost of replacement and lacking an ultrasonic cleaner replacement seemed easier. At least I’ve learned that fuel in the bulb is what’s been sucked through the carb (and is returned to the tank when you squish it) rather than fuel sucked from the tank on its way to the carb.

Tim