What size main jet for stock setup with full exhaust

[AMechEng]

Danny has my carbs and I was wondering what a good size main jet is to start out with on a all stock drive train minus a full length UFO 4-1 exhaust.
Thanks

 

[one2dmax]

Just the UFO system for now? No other jet kit work? 150 mains.

 

[AMechEng]

Ya Danny says they are 35mm Venture carbs. Everything is stock to my knowledge except for the UFO exhaust. So you think 150s will work well for the mains? Thanks Sean!