Tillotson HR metering discharge port check ball

The Main metering discharge port a.k.a "the little white checkball"

This little booger is a pain in the neck to diagnose; it is always easier to replace than to repair. The main metering discharge port can be viewed by looking into the carburetor throat or venturi. It is a small brass fitting that has a small white nylon ball that acts as a check valve. The ball is supposed to shut off the high jet circuit when pressure in the carburetor reaches a certain point. If the engine has a lot of use, or you have a bad check valve, the nylon ball may be deformed and not close or open the circuit correctly. Basically it gets stuck. This is common if your engine sat for a long period of time with no use.

Signs and symptoms you need to replace this: When the engine is running, it will idle prefect, build up RPM to the mid range then suddenly die. When it dies it will still idle fine and at low RPM's appear normal. You can usually look in the carburetor and can see the white ball trapped at the top of the brass port,. It should rattle in there easily if not, its stuck and should be replaced. You can temporarily free it by pushing on it with some safety wire but it will stick again in the future.

**If you need a specific part that you do not see here contact us directly. We carry all HR carburetor parts for Tillotson and can special order anything you need.