I have checked the manual and it says you can test the oil pump on 305 by placing it a pan of oil and spinning the top gear. Doing this I get nothing, a few small bubbles initially, then zilch. It has been awhile since I fooled with one of these marvels of simplicity. The pump is good and free, am I doing something wrong, too much oil level, not spinning fast enough, or has the pump gone to a better place. A search didn't really provide much help, just a number of real talented guys who modified this piece to work much better by machining new parts.........