trying to figure out a BF issue

[Dougie]

So I'm working on a 81 cb 750k.
My main jet is 110
Secondary is 75
I'm running the 4 in 2 stock exhaust
4 k&N pods
Compression is 120 on all cylinders.

I've tried taping the pods 75% arounf with 3.5 turns out on the mixture screws. The bike idles easy enough but tends to bog out when pull the throttle mid way and backfires quite significatly on the 1,2 cylinder side. I've tried adjusting the mixture screws in and out but still can solve the backfiring issue.
Do i check the timing next? Is the tape on the pods neccesary? What's next? thanks.

[Re-run]

The tape is to help the pods create the vacuum required for cv carbs to work right.

There was a long thread about getting pods to work, http://honda-cb750-s.456789.n3.nabble.com/I-GOT-PODS-TO-WORK-td4039223.html

Read that and see if that gives you some pointers.