Whoa! I just found Harrys "Carb Tuning 1998" document and it discusses the different SBN 44 models with different "internal drilling," ect..

I just bought an SBN44 setup for a Yamaha 701 from Summit that I thought I could simply re-jet, re-N/S and spring for a PP 550 starting with the usual:
100L 125H 2.0N/S ~21ish Popoff, etc...

Is this not the case??

I don't know if I have the wherewithal to **** around with the thing if the "internal drilling" is going to really throw the "traditional" settings off...