I can't unscrew the bolts on my Kohler 3386 rialto toilet to replace the toilet seat.

your nearest plumbing supply house...or try lowes

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.

there should be a nut on the other side use a socket, pliers, vice grips, etc. to hold it

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

Try a plumber supply house...where are you located?

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.

Enlargeing the holes will not turn out well.

Modify the seat to take the plastic bolts.


Hope this tip helps.

R/
David

Roberta3fan could be giving bad advice based on experience with other toilets. This does not seem to be an option for this toilet design. I am in a similar situation and it appears that the nut (and it is a metal bolt) is not what you would expect. Here is a picture of the anchor kit for this toilet seat: http://www.plumbingsupply.com/images/kohler-anchorkit-84999.jpg I am going to assume that the sleave that should be engaging the bolt is cross threaded and try to grab it with a pair of vice grips. I'll let you know if it works.

Give Kohler a call AFTER you read the instructions thoroughly. Good Luck, seriously.

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