Hi
I have exactly the same problem as you have with 2 mowers. One is a Haytor Sprite, and the other a Briggs and Stratton. They both use engines with similar carburetors. Both mowers will not prime, when the rubber bulb is squeezed repeatedly. The Haytor however will start if I squirt a small ammount of petrol into the carburettor intake before trying to start it. It runs for about 5 seconds and then stops. If, hovever I continue to squirt more fuel into the carburettor before it stops, it will run for longer, or until I stop squirting more fuel in. After about 3 or 4 attempts, it will continue running on it own, and I am able to cut my lawn.
The Briggs and Stratton mower also starts by doing the above, but will NOT continue to run, ever.
If you try this, use a syringe or similar to inject the petrol, DO NOT pour in it from an open vessel, as it IS petrol, and could possible ignite.
Lets hope someone else can throw more light on the subject.
Jack
Jack Rogerson
September 2007