I am all out of guesses here. My banshee is backfiring when you kick it.
Rebuilt carbs
120/105 comp
Finishing up leak down tester
Slides not in wrong carb
Fatty pipes
Pro design filter
Timing plate ( now set at zero) trying to make sure the advanced timing wasn't causing a problem.
I give up. Though I know 105 is low it still should run. I pulled the pipe on the low cylinder to look at sleeve it looks good.
Any suggestions on what to try next?