Always leak-down test your carb(s) After reassembly. Yours are leaking, so replace the needles and the seats.
To do a leak-down, pump pressure into the inlet nipple and put your finger on the outlet, pump up til a few psi's short of pop-off setting.
If it holds five minutes, the carb passes, and now its ready to go on the motor. If you have a rv cover in proper spec, the ski will be easy to lake tune. Use WD-40 when adjusting your needle lever. Read the Sticky, watch the vids, or go to Mikuni's website.