Hobbyfun100,

The YS60 is a pumped motor. The third line is the pressure line back to the tank. The screw inb the bottom of the case below the carb is your regulator adjustment screw. This screw should not be moved. It is set at the factory and RARELY needs adjusting. You will also notice there is no pressure nipple on your muffler, because the motor doesn't need one. YS engines, like the one you have are incredibly powerful motors and are favored by all of us here in this forum.

There are many more knoweledgable guys here in this forum who can explain the motor better than I have, but it's a start.

If you don't want to worry the motor, just send it to me. I'll be glad to take it off your hands...........LOL