At last, well almost,

Finally cut the yard with my Snapper 28 RER. Mounted the 12HP engine from the donor 33. Swapped drive disk/pulley from my old 10HP, now belt fits. Swapped starter gears. Readjusted drive disk. Started and cut yard while it was running, ran fairly well but would not idle. Pulled Walbro LMT carb. disassembled,cleaned everything, reinstalled. Now the problem. Screws set at 1 1/2 turns out, needs some fine tuning. How do I disable the seat safety switch so I adjust the carb while the engine is running? Thanks in advance.