Put the axle nuts back on but run them close to the wheels, not tightened. Run the kart a short distance at very low speeds. That may help break them loose. I've done this on cars with seized rims. Once the wheels "pop", jack up the kart and remove the wheels. Hope this helps. Good luck!
have you tried heating everything up with a torch yet? sometimes that will help.
Don't have a torch. Was debating an air hammer and block of wood.
As far as I can tell it only has the one nut on the axle holding it on. I scoured it for over an hour trying to find something else holding it on. Might try running it tonight with the nut loosened.
If they are like the Manco rims on my 2 seater, which I believe they are, the bearings are built inside the wheel's center... I wouldn't heat them, as you may ruin them.
They are probably frozen on the keyway, try running them loose as mention above, spray with PB Blaster, try trapping the rim's edge around/along the axle on the back side with a punch and hammer to see if they will brake loose.
---------- Post added at 01:33 PM ---------- Previous post was at 01:32 PM ----------
It is only the one nut. Keep working at it, it will come.
Air hammer on the back side will work too.
After a butt load of pb blaster loosened up the nut and told him to go run it around.he came back 5 minutes later with one loose. Told him keep doing it and added some more pb blaster and viola both were free and are now dressed up with new rubber. Thanks for the idea worked like a charm.