I have a riding lawmower with a B&S Vanguard V16 motor. The motor has nearly 500 hours. After the motor runs has warmed up, it appears to miss fire or hesitate as the motor turns over. I had a similar experience shortly after buying the mower new and the problem was diagnosed as a faulty dual igintion coil. The coil was relplaced and this solved the problem. Should I be looking for something electrical or is it a fuel problem such as a dirty carburetor? The fuel filter and air cleaner are new. Appreciate any ideas or suggestions. Thanks