My choke unit, the same as yours, leaked and the engine was difficult to start. I lapped the disc in tried to seal it but the shaft was very worn and managed to get a new unit. I had to change the disc as the new unit had the single row of holes. Stopped the leak but still didn't start well. It took many attempts at tweaking the choke cam screw to get it so it's much better. If I remember I have a lot of disc rotation ie fuel to start. Actuating the choke does also slightly rotate the throttle disc to allow air through and it's a balancing game to get it right. Another thing to worry about is the throttle cam, is it the correct one and/or worn. If its correct stay off the throttle and don't depress the clutch. Note the 8mm drill bit setting didn't work for me it was trial and error.
Good luck
Iain