Before we get into the nuts and bolts of the Honda 21-inch Variable Speed 4-in-1 Gas Walk Behind Self Propelled Lawn Mower we should point out that the model numbers HRX217VKA and HRX217K5VKA are used interchangeably by Honda to refer to this lawn mower and there do not appear to be any differences between the two. That said the best adjective to describe the HRX217VKA is powerful.
Consumer Reports recommends the Toro Recycler 20333 because of its very good ratings in ease of use handling side discharging and bagging and excellent mulching. The reviewer specifically liked the washout port for cleaning buildup under the sizable deck. The Wirecutter used to list the 20333 as the runner-up pick but supplanted it with the 20340 because of the newer models upright storage. However the reviewer still recommends the 20333 if the blade brake clutch is more important to you than compact storage.
After sharpening both sides of the blade place it on the kits cone-shaped balancer. If one side dips below the other continue sharpening it until the blade rests level. Return the sharpened blades to the mower and reattach. If you have a torque wrench its a good idea to use it here. Often you need to tighten the blade mounting bolt/bolts to a specific tightness level. Typically measured in pound-feet your instruction manual should list these specs. For example my personal machine the Honda HRR216VKA between 36 to 43 lb-ft of torque is required.