Carb pop off pressure 787 anyone really familiar help!!!!

[realmechanic2013]

I got a 97 xp new top end and rebuilt carbs and motors back firing bad at high set to 0 low set to 1 3/4 and timings right .... I think pop off is wrong and waiting for meter to test pop off anything els it might be ???

 

[mikidymac]

Backfire can be causing be wrong rotary valve timing and leaking needle and seats.

Is it backfiring through the carbs or out the exhaust?

You should be running new 1.5 needle and seats with the 95 gram dull silver springs.