I have a 6 H.P. 'Rude that I had the same identical problem with. Was hard to start but ran great after it started. Tried everything, even a total rebuild. Had the same issue after wards. Turned out that the choke was not staying closed 100% when I pulled the knob out. Found that when I let go of the knob, it was going back in just a tad, the choke plate was opening just a wee bit, but enough to make it hard to start. I ended up just putting a pin in the choke knob to hold it into place (all the way out) when I pulled the starting cord. (I first tried to adjust the choke linkage to accomplish this, but that did not do it). Once the motor starts, I pull the pin out of the choke handle and push the handle in opening the choke. Not that tough of a job to put the pin in & out, & I have it tethered to the motor so I do not lose it. Works great to solve the hard to start problem. Once it starts, it is good for the rest of the day.