Okay penetrating oil will not work period. The oil swells the dirt and rust forming a seal off area.
Try this instead provided you have not beating beating the shaft where the screw goes.
- Get a schedule 40 3/4 PCV coupler.
- Cut it nearly in nearly leaving leave the center stop intact.
- Now here is the tricky and heat maybe needed, drive the end with the stop ring on the rim standoff. Heat will soften the plastic but use no more necessary. You are wanting a very tight fit.
- Turn rim and if necessary the mower up where this becomes a cup.
- Fill with with 2 cycle fuel mix and let soak in. You may need to refill the cup a few times.
- This usually loosen the rust up.
- If this don't work the last resort is to try Muriatic Acid. It will eat away the rust. Just got get the past swelled rust area. Careful don't breathe the fumes. It can take your breathe away. Also don't get it on anything aluminum. Once the rim is off neutralize the acid with water and immediately oil things to prevent flash rusting.
Note this may or may not work but is worth a try.
After the plastic pipe is warmed and pressed onto the rim I use shoe goo to seal the pipe to the rim and then install a 90 degree plastic fitting onto the end of the pipe. the 90 does not need to be glued. Fill the 90 to hold the penetrating oil. heat behind the rim to help the penetrating oiul flow into the rim's rusty collar/axle area.
And then I usually have to heat the rear of the rims collar with a torch and maybe use a HF puller and 3/8 bolts through the 2 holes in the outer part of the rim. Protect the end of the axle from being mush roomed
Do not beat on the rear of the rim or you can ruin your transaxle. (axle keepers inside the xmission)
I've had to just cut off some of them rim and then use a bearing type separator on the rims collar and install a new rim and antisieze.. Let the air out of the tire BEFORE using any heat.
The hydrostatic have a N adjust usually located under the right rear fender.
And when they won't go into N with the pull rod push them with one rear wheel off the ground.
Not a fun job when rims are rusted to the axle.