Hey chrisg....
you have the BN40I-38 carb...main=167.5/pilot=75...n/s-2.0..36-40pop off psi...LSA=1, HSA=0
You mentioned about motor being new/rebuild, think'n carb can be gone thru, also check fuel lines, inline filter, fuel valve selector, ...BUT most of all, think'n your ROTARY VALVE is off timed..