main jets don't have clips, taper jets do....
Taper jets control the mid range
What was the bike doing before you pulled the plug? idling, mid range, WFO up a hill?
I would tend to suspect;
A. a leaky vacuum petcock
B. a leaky float valve / crud on seat.
C. mis-set float height
Z. one side needing a different taper needle setting than the other.
Dump your float bowls in a catch container, run some gas through with the prime setting on the petcock, what's in the bottom of the container? You cleaned everything already? Do it again, trust me on this.
Dirty DIY trick; a quart oil bottle cut top to bottom so you have a narrow long catch bottle trim till it fits under the carbs, will make draining float bowls in place possible.
Not trying to be a smart ass, really, it's easy for me.