There's nothing more annoying than getting ready to mow the grass and the lawnmower either won't start or cuts out. I found a couple of products that are a must have in my shed now. Engine starter spray (liquid fire) and another product, Sta-Bil, that's added to the fuel and stops the engine from cutting out. Just follow the directions. (I found both at Walmart)
Note: prolonged use probably isn't a good idea according to comments online.