Mowing: Not Quite!

Feeling a little better today, although still dosed up with painkillers, I decided I was well enough to mow the upper lawn (the lower lawn and other parts of the garden are still too wet), with the ride-on lawn mower. I had checked it over and made adjustments before putting it away for the winter, so I expected no problems; not so. For some reason, which I have not yet found, it keeps cutting out, although spark, fuel and air are all perfectly satisfactory. I can only assume that I have a valve, which is occasionally sticking, there are two options for curing this, strip it down and sort it out or just run it until it frees on its own. I have chosen the latter and await to see what happens.