They rust on if not removed regularly and greased or coated with anti-sieze.
My method
put a pair of scissor jacks between the wheel & mower body to push the wheel off.
Only do them up finger tight +1 turn
Then Hit the axle( I use an air hammer ) till the jacks drop a little
Retighten jacks & repeat whole process.
Some can take a whole day to do.
Bo not apply too much pressure on the wheel or you will rip the axle right out
heat helps as will your favourite penetrant .
Rotate the wheel till the key way it us so you can squirt penetrant down the key way.
Some times I have to clean each little bit of exposed axle then apply penetrant to it , tap the wheel back on fully, have a glass of my favourite liquid then come back & do the whole thing again from the start.
Ahh yeah, that's not going to work on a walk-behind mower.
I assume you have successfully removed the bolt? The wheel should slide off as did the other one. What you may be dealing with is debris build-up behind the drive pinion and wheel. A little patience and wiggling should set it free.
I had the same issue on an older HR21. The wheel and bearings were nearly welded on with rust to the axle. I had to apply PB Blaster for 2 days while making sure it was penetrating well and with some force it finally came off. Tilt the mower on it's side so the PB sits and puddles up on the areas you want it to penetrate.
