I made a terrible mistake. I made a generalized statement. I know better. I should not have said that lawn mower engines would not start without a blade. I should have said that we once bought a used mower that looked great but had no blade. We tried off and on for two days to start it but could not. We than called a friend who owned a small engine repair shop and explained the problem and described the mower. He got quite a laugh out of it. Told us he would be glad to donate the parts to fix it. Showed up in just a few minutes with a used blade that he bolted to the crankshaft of the engine. It started right up and ran pretty well. I understand that larger engines have flywheels and will run without a blade, but there are some (at least one) low horsepower engines that will not start without the blade to act as load. That certainly is a better comparison to an RC engine than a 20 hp riding mower engine or a 75 hp outboard engine.