I have a C-121 8 Speed (12 HP Kohler). Tractor has been a little hard to start lately, and I sometimes have to use ether to get it to start. this Tuesday I mowed for about 3 hours, and then the tractor quit like it ran out of gas. Could not get it to start. I let it cool off & the next day I removed the fuel line from the carb. I then tried to start it to see if the fuel pump was working. it seemed to be working as there was fuel flowing out the line. I re-installed it to the carb and tightened all fuel line clamps. I started it and mowed for about 3 hours when it quit running again and would not start. I looked at the Kohler fuel filter and there was no fuel in the filter. So I'm thinking clogged fuel pickup screen (In the tank), or maybe the fuel pump is getting to croak. The engine is 12 horse Kohler, model K301AS, Spec. # 47648d. Thanks for your help. WH Doug