Check out eBay item # 201663276172.
2 Manco steering wheels, one just like yours.
One of the pics shows what yours looks like where it slides on the steering shaft.
You need to prop the kart up so that you can repeatedly spray PB Blaster and let it soak down into the collar for a few days.
Then you take an open end wrench that just fits over the shaft and butt it against the underside of the wheel and smack the wrench with a hammer as close to the shaft as you can get.
Tap on the shaft close to the wheel some before you smack the wrench with the hammer, it may help loosen the wheel.
If you have a bigass adjustable wrench, that would work even better than an open end.
You'd have more contact area and you can smack it harder.
Of course, if you miss you might knock the roller out of the wrench but you can't have everything!
