When start engine first 15 seconds ok then engine starts to rev up and down Removed plug found sooty Cleaned up refitted Resarted ran 15 seconds ok then started to rev up and down
I call it engine hunting
Have cleaned filter still same
Can you please advise
Regards Terry

Terry, November 2011

Bet you have a briggs engine with a diaphragm carb fitted (the type where standing behine the machine the carb is to your right on the side of the engine and is connected directly to the top of the fuel tank.

If so, then your problem is simply the carb diaphragm that needs replacing. Obtain part number 795083 from briggs and stratton for around £2 or £3 pounds and go to you tube to see a video of how to fit it. Very common problmem and easy to cure.

pleasant, November 2011

Indicates fuel/air mixture. There will be an adjusting screw on carb., usually with a spring under the head. Try adjusting it, say half a turn at a time. Try in both directions.

davidj, November 2011