When I use my MudRunner®, why does the joint compound flow out very slowly?

Your joint compound mix is probably too thick. Try mixing more water into your compound. Generally, about 28 to 30 oz. of water per 5 gallons is the right mix. The rubber wiper inside of the material cylinder may also need to be lubricated with Ames Bazooka Oil. This wiper will sometimes become dry and slows the movement of the piston that pushes the joint compound. This will keep your MudRunner working effortlessly.