Some lawn mowers such as the Craftsman 37705 have a washout feature. It is essentially a garden hose fitting on top of the circular blade cover. This allows you to pump water into the blade assembly while running the engine. That action is designed to flush dirt and grass debris right out.
Your Best Digs also recommends the Sun Joe mower but the reviewer also added a number of caveats. He found it will get the job done if you prefer to only bag and just have $100 to spend. However the clippings compartment filled up quickly for him. And the height adjuster felt flimsy and required adjustments on each wheel.
EGO has two 21-inch deck 56-volt lithium-ion cordless battery mowers that are quite popular and share a number of similarities: the LM2101 and the LM2102SP. The major differences between the two are that the LM2102SP is self-propelled has a larger-capacity 7.5Ah battery and it costs $100 more. For the purposes of this review we are going to focus on the features they share in common.