If u have to use the choke constantly, its prolly not too rich. maybe too lean. my engine used to bogg wen it was wya lean. fuel pump maybe? turn the mix screw all the way in, back them out 1.5 turns. thats a good starting point with those carbs, also check fuel pressure, 3psi is the right pressure i think, if ur high or low with those carbs, it wont wanna run right.