Motorcycle Repair: Honda Rebel 250cc carb sync, cv carburetors, mercury manometer

Question
I have a Honda Rebel 250cc special model which has two CV carburetors,recently i overhauled the cylinder boring to a larger size.Now th piston size is .75.The air and fuel mixture is not the same anymore.I do not have a mercury manometer or other carb  balancers.How can I balance the mixture of both these carburetors?

Answer
Syncing the carbs is not balancing mixture but balancing the throttles to match the vacuum from the cylinder. You can estimate the throttle balance by turning the balance screw and shining some light down the opening. You want to get them about the same: the sliver of light should be about the same for both carbs. Once they are balanced you should be able to start the bike (on choke) and tune the idle mixture and the idle RPM set screw, so that it will idle off choke (once its warmed up). You still need to use mercury sticks to do a proper balance for smooth idle and operation.