1. Side mounted oil breather gasket. Oil rarely leaks from here unless too much oil has been put into the engine.
2. Sump gasket. Remove the engine from the equipment and replace the sump gasket.
3. PTO oil seal. This is another rare problem. Purchase a seal puller and replace the seal.
4. Sump bolt has worked itself loose. I have seen this happen to lawn tractor engines. Remove the sump and replace the gasket.
5. Crack in sump. This only happens if you hit something big and really hard. Sump must be replaced.
6. Oil fill tube gasket broken or missing. Replace this o-ring or paper gasket.
7. Dipstick tube problems. I have seen it where replacing the dipstick o-ring gasket will not work. This is due to a deformation in the dipstick tube. Replace the tube and the problem should be cured.