If the gas tank outlet is mounted above the line of the fuel inlet on the carburetor, you probably don't have a fuel pump. If the fuel tank is under the seat and rear fender area, then you will have a fuel pump, to lift the fuel to flow into the carb.

I recently pulled a push mower out of the garage. It had been sitting 2yrs. I removed the drain plug from the carb and drained it. The gas tank was empty. I filled it with fresh gas and primed the carb. It would only run 30 seconds or so. After a few failed trys, I pulled the carb and removed the bowel. There were no foreign materials or bad gas. However, I found the float pin was actually stuck in place due to a gum coating that formed from dried gas. Point is, you might need to pull the bowel from the carb and check the function of the float and float pin.

Shucks, I accidentally hit submit . .................................................... Are you quite certain that the gas you are now discovering, was not already in the oil from before you undertook this rebuild? What may be damaged depends on how long the engine "ran" with contaminated and diluted oil. If the engine had been running with gas in the oil before the fuel pump work, I would expect the exhaust would have had a definite blue or blue-white color "smoke" in it. In which case, the most likely components to suffer damage would be the crankshaft rod journal and connecting rod, the piston and cylinder walls might have sustained some "scoring" or galling, but usually, the piston and cylinder of a 4 stroke engine, are "spared" in cases of gasoline contaminated oil in the crankcase. It usually requires that these engines be "run without any oil" before the piston and cylinder walls see damage (of course by that time, the crank and rod is usually "trashed" as well). Consider a 2 stroke engine escapes damage to the piston and cylinder with as little as 1 part oil to 50 parts gasoline. Also consider the the same amount of oil is sufficient to lube the crank main and rod journals in a 2 stroke engine, but ONLY DUE TO the 2 stroke design using ball or roller bearings in those 2 places. Plain bearings in the typical 4 stroke OPE engine will NOT survive long if run with diluted oil. If all the time this engine has actually run with gas in the oil, amounts to a mere 20 to 30 seconds, I believe all you have "suffered" is a solvent washing of the interior surfaces of the engine. Post engine numbers and let's see if we can find some illustrations of that carb. Maybe then we can retrace your steps during reassembly of the pump.

Ok, you've confused efficiency with actual cost. Very easy to do. Gas will always be the least efficient, because some of the heat is exhausted out thru the flue of the home. When natural gas is burned properly, the exhaust is carbon dioxide and more efficient furnaces will also produce some condensation along with that carbon dioxide. (CO2) When there is improper combustion the furnace can produce carbon monoxide. (CO) In most instances of this there is a lack of combustion air, improper installation etc. A heat pump will never produce any exhaust 'at the home' of which it is installed. Heat Pump efficiency: there is no exhaust 'at your home' to run the heat pump. Depending on how the electricity is produced in your state. Some power plants use natural gas for power production... so in reality there is 'efficiency' losses thru waste or exhaust fumes. Dual fuel options: Prices change over time and thru various times gas costs can run higher. But with large recent discoveries natural gas will likely be the cheaper option, especially for areas that have average daily temperatures below 32 degrees. A heat pump loses efficiency due to running defrost mode when temperatures are less than 32 degrees out side. If your electric rate is high in your area then you would likely pay more to run a heat pump than you would a natural gas furnace. Heat pumps mainly exist for those who do not have gas available in their area, as compared to electric strip heat the cost effectiveness can pay for the heat pump within a few seasons. Typically in a electric strip set up for an average home you could have 4 heat strips that run 20 amps per strip. Under full load that is 80 amps. In comparison a modern day heat pump running in heat mode may use 10-15 amps under full load. Those operational savings in comparison to electric strip heat add up quick.