I have a Kohler one piece, low-profile toilet - not sure of model (came with house which we have owned for 18 yrs). While investigating why there is always a faint urine smell coming from the bowl, I discovered that no water was running from under the bowl rim during flushing, so the top of the bowl essentially was never getting cleaned. When I pulled off the top of the toilet to investigate, I found that there is a thick hose that leads to the area that feeds the rim but it was above the water level in the tank. Problem is, if I adjust the valve float to raise the water above the hose, the tank fills, the water overflows into the rim and cleans the bowl, but of course the level then drops and the valve starts to refill the tank again. For the life of me I can't see how the rim flushing is supposed to work. Insights anybody?
After doing some more research, I answered my own question. Fluidmaster is very deceptive in its claim that their 400A valve "fits" both 1-piece and 2 piece toilets. Yes, it "fits" BUT IT DOES NOT WORK THE WAY IT IS SUPPOSED TO! One piece, low-profile toilets have the tank water level below the rim of the bowl and require a special diverter valve that initially directs water to the rim when the flapper is open and then switches to filling the bowl when it is closed. If anyone is interested, I just ordered one (the LASCO 04-4165 Coast 1B1X) for $22.50 from Amazon.
Pictures might help. There is usually a small pipe from the fill valve that runs into the overflow tube to add water to the bowl after flushing, as the tank fills. If your toilet works as described, perhaps it should be pointed into the "thick hose."
Otherwise I'd have to suspect that the thick hose is not going where it should be, or is not connected as it should be, but not having your specific model of toilet it's hard to guess.