I believe that the first approach would be to make sure you have an adequate fuel supply. If the tank is rusty inside it needs to be drained & flushed to clean it. The fuel tank on this model is an intergal part of the frame. Look under the frame at the tank and you should see a flush type pipe plug with either a square or hex female drive. This plug can be tough to remove, but, it will allow you to drain & flush the tank of any loose material that could be plugging the pump intake. The other suggestions are good too. However, regardless of head gasket or anything else if it's not getting enough fuel it will not run as it should.
Also, you may want to start the unit and with it running spray some type flamable fluid around the intake manifold gasket. If the gasket is bad this will cause the engine speed to increase.
Spray parts cleaner works well for this...just use adequate ventilation and do not breath the exhaust fumes when this stuff is burned.