I wish I understood lawnmower carburetors. I mean, I don't REALLY understand care carbs either, but I at least get the concept: There's a linkage to the fuel line and the throttle so when you step on the gas pedal, more fuel-air mix gets sprayed into the cylinders and the engine revs up. Push lawnmowers have one speed: on. But there's definitely a carb and a throttle. I guess it must be engineered in some way to give the cylinder more fuel-air when the engine is working harder, but who knows how that works. There's a linkage you can see if you take off the air filter. And a light spring that holds it in an open position but it's all very strange.
I mention this because the verdamnt engine is back to doing this low rpm thing. Lately I've gotten it back to normal rpms by tilting the front wheels all the way up in the air and holding it that way until the rpms pick up. No idea how or why, but it worked--until today. Added wrinkle is, it seems to run fine if I run it all the way out of gas--or if the engine dies from hitting a heavy patch of grass or something--but it I'm done mowing in one spot and let go of the deadman switch to kill the engine, when I restart it it does the weird low idle: Brrm....brrrm....brrrmmm...bbrrrmmm....putputputput....brrm...