need help with stock mikuni carb for 88 2,6l

[FMS88]

Good point, SubGothius. Tomco is one supplier that calls it a choke pull-off. Their P/N is 7404. Unfortunately Tomco doesn't list the disc, but it can be acquired by purchasing an entire vent valve kit for $200-300 depending on the jobber. The current P/N is MD617185 (previously MD612742). At that price, might just as well get a Weber.