I have 3 walk behind mowers all with the Kawasaki FH541V KAI 17 hp engine. 2 of the engines start on first pull everytime. The 3rd one takes 5-6 to start in the mornings and after it sits for an hour or so and cools down. I've tried choking and not choking and both are same. The only difference with the engine that doesn't start as easily is that it hasn't been used as much. The 2 engines that start well we use almost everyday. The engine that doesn't start well only gets used about once every 10 days or so. I've replaced the spark plugs but the old ones looked fine. The engine that is hard to start only has 20 hours or so on it but it is 2 years old. Please help.