I have a two year old snapper 11.5 HP pull start machine that starts and runs perfect on some days but after running it then shutting it off it will not restart for a half an hour or so. some days I can not get the machine to start at all. it has fresh gas and new fuel filter and new plug. when it starts it runs perfect. no grass plugging things up and safety switches are all working properly. the snapper dealer in my area is not very good and has never had such a problem and can not help me unless I spend a lot of money sending it to him to fix. I need help!