The Rialto toilet makes it very difficult to replace the seat as you cannot access the wing nuts which in a moment of engineering genius you put inside the bowl I have already purchased a French seat to replace the broken one but it is not easy to get the old seat our or secure the new one

Wrap a putty knife with a wash cloth, and push it between the toilet ceramic surface and the plastic hinge for the seat. Wedge it in there. Now try unscrewing the hinge screw. This provides back pressure against the hidden nut on the other side and may let you successfully remove the screw.

I just had the same problem.I can not believe that kohler would design such a flaw. I have four of these toilets in my house,and it would be ridiculously expensive to replace, especially for a seat. To fix it I went to OSH and got some 1/4-20 T nuts, went home cut the bolts off the seat (multi master dremel) with metal cutting blade. With a screw driver tapped the bolt and the small area around the bolt down into the toilet area. Now you have just a porcelain hole. Clean area with solvent (lacquer thinner),get some gel type super glue from hobby shop and put it on inside and top edge of the hole on the toilet. Put some glue around the shaft and under side of the T nut and slip it into the hole.Then put a SMALL bead of glue around where the T nut makes contact with toilet and let it dry aprox 1/2 hour. Now you have a permanent fix.To prevent a problem getting the bolt out in the future,put some anti seize (auto part store) on the threads of the new bolts. Hope this helps.
Good luck
Max

there is probly caps on the hinges or if not just directly underneath there should be a nut.
1. pop the caps off with a butterknife or whatever 2. get a flat head screwdriver to hold screw 3. use a socket to turn the nut underneath.
good luck

Consider using a toggle bolt (with wings) and a large stainless steel washer to re-attach the seat.

Kohler will try to sell you $46 anchor bolt kit 84999 & also there special tool. You should expect that for a $400 toilet.

Try this instead:
1. Use 1/8" drill bit and drill and drill around the bolt until the anchor material can be removed.
2. Carefully clean hole with 11/32 drill to remove all remaining acchor material.
3. Go local hardware store & buy a 10 - 32 3/8"X3/4" rubber expansion plug (make certain threaded part is brass & has shoulder on 1 end), a 10 - 32X1.5" Phillips bolt and couple of small fender washers fit the seat.(about $4 for 2)
4. Assemble carefully not to over tighten and crack the porcelain.

Hope it helps

I repaied one of these laast week and it had the Plastic nuts in between the webbing on the seat where the lid connects I believe You remove the plastic cap with a knife and use a flat tip screw driver to remove the screws and replace the seat.

There is clips where the bolts should be .Flip the clips up grab hold of the seat and pull it strait out towards the front of the toilet.

Here's what I did. Unscrew them as much as possible. Then I used a bolt cutter and hacksaw to cut away as much of the plastic seat holders as possible. I could then remove most of the seat, and get better access to the screws. I then raised the loose screws enough to cut them with a bolt cutter. Soft screws cut easily. The screw heads are now out. Now, tap down on the screw/anchor and it falls into the bowl. It will stay there. The remaining problem is that you need anchors to secure the new toilet seat. Kohler wants $50. I have a usable but loose seat. Never again-Kohler.
I strongly recommend using a boltcutter. A hacksaw will tear up the bowl.

to access the nut remove the tank lid, then go down and forward, its there.

If your problem is like mine your toilet seat is loose and swivels when you sit on it. If you try to tighten down the screw it won't tighten. Use instructions above to remove old hardware.

To fix with new hardware

Purchase Hilti brand 3/16" x 2-1/2" Toggler Brand Toggle Bolt (Home Depot sells the kit). Kit comes with 10. You will only need 2. My last repair lasted about 8 years (with new kit = 40 years left or the purchase of a new toilet - whichever comes first). Set comes with 3/16 flat head screws. I recommend purchasing 3/16" 2" round head screws with matching flat washers. Sink Metal Toggler into hole with toggler pointing straight up (it's attached by long plastic legs). As it goes in the hole it opens up. Pull up on the plastic pull rings as tight as you can until the toggler is tight up against the inner porcelain of the bowl (similar to tightening cable ties). Line the seat up with the holes and it's new plastic adapter (that won't slip into the hole courtesy of Hilti). Slide washer underneath round head screw but on top of toilet seat assembly and screw directly into the newly installed toggler which is sunk in bowl/abyss receptacle. Repair should take around 5 minutes.