The usual troubleshooting suggestions for this kind of problem are to check the fuel lines and clamps; clean the carburetor; put in new spark plugs; check the battery charge and install a battery shut off if not in use for long periods of time. To draw fuel up quickly, remove the air filter, place your palm over the carburetor and rev the engine. Some suggest starting with the sparks plugs first, but if these other items are even marginal and contributing to the engine-start difficulty, they might go overlooked if the spark plugs are thought to be the whole problem.