The lawn mower is a Noma with Briggs & Stratton 3.5hp engine. The spark plug has been cleaned and it has both oil and gasoline. I prime the motor and it starts but then dies. If I keep pushing the prime rubber button the motor runs but as soon as it is left alone it dies. Why?

Charles, May 2008

Bob and Phil thank you for your suggestions. I will be working on the motor tomorrow (Friday 29th),

Charles from Toronto, May 2008

more than likely its your diaphram/gasket that fits between the carb and petrol tank.Take your engine No. to the dealer and get a new one.It only takes two bolts and five screws to get at. Careful with the gasket as it comes in two halves and dont lose the spring thats in there. Clean the little filters and put it back the way it was not fogetting to connect the throttle spring as you put the carb back on

Bob from england, May 2008

If it's the carb-on-on-the-tank model, I suggest that there is either water in the tank (left out in rain), or the pick-up pipe in the carb is blocked.

It's also possible he carb diaphragm is holed - while the carb is out you may as well replace it.

phil_saunders@bigfoot.com

Phil Saunders, May 2008