One of the biggest problems with small engines is the age old problem with hard starting. Back in the old days, before electronic ignitions, it often was the result of points being out of adjustment which threw the ignition timing off and all the other fun problems that went along with that. But points are (thankfully) a thing of the past unless you are into vintage machinery. Since the 1980's almost everything is electronic ignition of some sort. Because of that innovation having to adjust timing on a small engine is a thing of past. So, why is it that small engines get hard to start? There are lots of things that can impact an engine's starting ability, but the two most common problems come down to maintenance. In many cases the problem lies either in the fuel system or in the valves, sometimes both. Today's fuel is typically a some sort of ethanol blend; nothing new there. But, what most people don't understand is that ethanol is a form of alcohol which is water based. Think back to your high school chemistry class, "like dissolves in like" alcohol mixes better with oil based products than water, but over time it separates and then begins to break down. Once fuel begins breaking down it starts forming corrosion on the metal parts, particularly the brass jets. The jets get plugged and don't allow fuel to flow through and wa la, your machine get very hard to start and often will not idle. The best solution is to buy non-ethanol fuel, however depending on where you live that is not always so easy. So, if you know your machine is going to be sitting for a while, drain the carburetor and fill it with Sea Foam, or even diesel. Just remember to drain the fuel bowl before trying to start it the next time.
Valves are the other common culprit for hard starting. The reality is that valves go out of adjustment with use. Often we don't think about adjusting the valves because modern passenger engines (like in you car) use hydraulic lifters that compensate for wear and don't generally need to be adjusted. You do occasionally see hydraulic lifters in small engines but not very often. When valves go out of adjustment it is the opposite of what you might expect. Instead of the clearance between the valve and lifter getting loose, it actually gets tighter; to the point where the valves are not actually closing completely. This prevents the engine from building proper compression (particularly when the engine is cold) making it very hard, if not impossible to start normally. Tolerances on modern engines, particularly high performance engines, are very tight so a few thousandths of an inch can be the difference between starting and not starting.
As spring approaches and you start thinking about getting your equipment out of the shed keep these two things in mind. A little bit of maintenance can save hours of cussing.