I have a Sears Cylpso heavy duty dryer. The dryer heats up but the clothes are still damp. Somethimes I need to run it for over 2 hours to get the clothes dry. Is there something I can do myself to fix the problem?

Have you checked for any lint clogs in the discharge pipe? Usually when my dryer takes way too long to dry the culprit is always excess lint build up in the discharge vent somewhere. Good idea to check and clear out the vent every so many months because if you do not do this you could have a possible fire in the vent pipe due to all the lint.