Quick carb question

[chiz]

 My Yam triple carbs are syncronised to carb #2 there is no sync for carb #2. My service manual for FJ says 1 and 2 are synced to each other using screw A and 3 and 4 are synced using screw C.  I dont get the part where screw B is used to sync 3 to 1 seeing as though 1 and 2 are pulling the same vacuum as 3 and 4 can someone explain why 3 to 1 needs to be done? Thanks Lez

[Pat Conlon]

1 & 2 are synced together, call them left bank (as you sit on the bike)
3 & 4 are synced together, call them right bank

Then via middle screw, Left bank is synced with Right bank.