Cable Maintenance for Dump valves

I've never installed a new dump valve and I have never seen instructions for installing them. I have had to take mine apart. Most recently this week for repairs from a tire blow out that broke off the end of the drain. One thing I noticed is if you over tighten the four bolts that hold the valve together, it will be hard to open and close. If somebody did some work on yours the bolts may be too tight.
If nobody worked on it you might be due to replace the valve. Really not that hard to do depending on the location under the trailer and the creativeness the factory used.