I am having some problems with the 15hp vtwin kawasaki engine on my Metrohp. When the mower first starts up it runs like **** for about the first two minutes of use. It runs very loud and gives off kind of smell. It seems to run at a lower Rpm also. After about 2 minutes of use the engine kicks in and runs perfect as if nothing were wrong. It runs badly for the first minute or two every time I start it. Once it kicks in though I have no problems. I have cleaned the air filter and air screen. I have replaced the fuel filter, oil filter, and spark plugs. The mower is about 1 1/2 old. Do you have any idea what the problem could be? What else can I try before taking it into the dealer? Do you think it could be bad gas?