Originally Posted by bblueser
Please describe the differences between the two Honda lawnmower models noted in the title.
What has changed on the choke, and/or the carb?
What is the correct amount of oil to add to my HRX2173hya when changing the oil?
• The HXA has a manual choke control.
• The HYA has Auto Choke (automatic choke).
• It's hard to say for absolute how much oil to add, as it depends on how completely the old oil has drained. Make sure the height adjusters are all set to the same point, and the mower is on a flat, level surface when checking the oil level. Start by adding 12 ounces, then use the dipstick to check the level. Continue to add a small bit of oil as necessary to bring the level of oil visible about midpoint on the hashmarks at the tip of the dipstick.
Caveat: I work for Honda, but the preceding is my opinion alone.