Before trying to start the engine of a Cub that has sat for a period of time (perhaps months, certainly years), it is necessary to prime the oil pump to make sure oil is pumped the moment the engine begins. Failure to do this may cause damage to the engine. It is suggested to replace the old oil filter with a new one while doing this task. Use a Wix #51153 or equal. Oil used to prime the pump is the same oil in the engine or you're planning to use.
- The oil filter housing is located on the right side; between the magneto or distributor and the gas tank (highlighted below). Open the top of the oil filter housing by removing the center bolt and cap.
- Remove old oil filter and rubber seal ring (if present).
- Clean housing lip and underside of cap. Depending on the condition of your oil housing, you may want to clean the inside. There is a drain pipe extending below the housing.
- Inside the housing, find the small diameter hole in the back (highlighted below).
- Using a small oil can with a flexible spout, insert the tip into the hole and pump some oil into it until oil overflows back into the filter housing.
- The oil pump is now primed.
- The holes in the top and bottom of your new oil filter may not be the same size. Use your center bolt to determine which way the filter is supposed to go, then insert the new oil filter, rubber seal ring and top. Secure top with center bolt. Wix and some others have the rubber ring included in the box, others like Fram may not. You may have to clean and re-use the rubber seal ring if in good shape.
Hope this helps new Cub owners how to prime the oil pump.