Mansfield Flush Valve Does Not Empty Tank

Troubleshooting a no flush intermittent problem.

I have discovered that I have a Mansfield flush valve in the kitchen toilet and that when flushing the toilet only about 1/2 or a little more of the tank is emptied. If I hold down the flush handle until the flush stops, then the entire tank empties. Should this valve allow for the tank to mostly empty? If so, then what typically goes wrong with these valves to where they impede tank emptying?

Thanks for any assistance.

The Mansfield is a dual flush toilet. 1.1 gallons on the initial flush, and 1.6 gallons when the handle is held down. We have discussed these dual flush toilets here in the past. They work well but how do you tell guests that if they go # 2, to hold the flush handle down?

http://www.mansfieldplumbing.com/wp-content/uploads/2015/03/4384CTK.pdf

Wait....kitchen toilet? That's genius!

Dual Flush!!! Thanks Havasu.

Yes Matt....the toilet sits right next to the trash compactor.

First time I have ever heard of one of these systems. Sounds pretty interesting.

I have only recently seen a DUAL flush valve on a Mansfields toilet. That is a new thing for Mansfield. take a picture of it. Comments about dual flush maybe misleading. Older Mansfield toiles have a single barrel that lifts up when flushed and drop back down as the water exits the tank. It is normal for a 1/3 of the tank water to remain in the tank after a flush.