I cleaned the carburetor and replaced the carb gaskets, and replaced the spring underneath the governor air vane. After putting it back together I adjusted the rich/lean screw and turned the collar under the air vane clockwise to bump up the RPM. The mower is cutting fine and I get good response from the self-propelled. I do not have a tach, and I suspect that I do not have the RPM cranked up as high as supposed to be. But since I don't have a tach I am worried that if I get them too high it will be bad for the engine, correct? Is there any harm to the mower in running it with the RPM set below spec?