I have a Kohler CH20 on a Walker mower (64554 spec). Kohler parts breakdown says it needs a 24 559 11-S mechanical fuel pump. In the breakdown, I only find the complete pump. Can I buy just the diaphragm?That is all that is wrong. Otherwise, I searched on net and can't find the complete pump part listed. Has it been superceded? BTW I feel very fortunate because I just had this motor rebuilt and put it back on the tractor. The carb had no fuel. Someone told me I better check the crancase for gase. NO much had come into the oil, but you could smell it on the dip stick. That would have ruined the engine if I hadn't noticed. I will replace the oil and the fuel pump.