Have a 18 Hp MTD mower which won't start. Does not get gas, tank full, new gas filter, and new spark plugs. Has two kill switches on it.

OK, need full info... is it a side valve? Or ohv? Apposed cylinder engine, or a v shaped? How do you know its not getting gas? You can take the fuel line off at the carb, hold it with needle noses shut, then let it go in a gas can to see if it flows good, if it doesn't, clogged gas line maybe, or tank has trash restricting flow (most have a mesh screen in them, they get clogged) right where the gas line hooks up. If that's not it, try a little gas down the carb or starting fluid, if it runs and cuts out after it uses it up, carbs at fault, could be a stuck float if it uses a float type carb, or some trash did manage to get in and clogging, that or it was stored with untreated gas and gumming the carb... or if it uses a fuel shutoff solenoid on the carbs bowl ( listen for a little click when you turn the key if its working) may not be working. Also find the main kill wire to the ignition coil, take it off, to make sure the safety switchs have nothing to do with it.