I just looked in my book. The 26's had,
Fuel Level 3mm
Float level 22mm
Main jet 115
Jet needle 5DL31-3rd
Needle jet O-6
Cutaway 1.5
Pilot 17.5
Air screw 1 3/8-1/4
75 28mm
Fuel level 3.5mm
Float level 26mm
Main jet 112.5
Jet needle 5J9-2nd
Needle jet O-8
Cutaway 1.5
Pilot 17.5 Air screw 1 1/4
The earlier 28's had P-8 needle jets, 2.5 cutaways, #20 pilots and 1 1/2 on the air screw. They were too rich from the factory. When I got my 75, I took it to Exhibition Engineering so they could dial the carbs in better. I'll have to check the needle size he put in them.
I know these specs are for a 903 but it shows how to make them richer without jumping to a bigger jet size.
Steve
