John Deere get 275 hard to start and will run bad like a fuel problem, not continuous

Hi I have a John Deere get 275 mower with air cooled 17 horse Kawasaki motor. The motor started to leak oil so I changed the crank case gasket and the oil seal on the bottom end by the clutch, this worked we fixed the oil leak. But once and a while when I mow it starts to run real crappy like it is starving for fuel and when I start it the brand new battery can barley turn the motor over. I read on a forum that the valves could be out of adjustment so I adjusted those and it is still hard to start I don't know if it is the automatic compression release that is not working or what. Thank you