Borbin the 🐱

The Mikuni carbs do not have a vacuum port to sync carbs.
Carburetor synchronization is important for a smooth running engine, and if you follow the simple steps, you can easily add a sync port to the Mikuni carbs.
The flat spot is perfect for the connector port.

I made the connector out of bronze with M4 on the outside and M3 for the cap screw. Use a 3mm or 1/8" drill bit for M4 as this material is very soft.

Depth is about 5mm.

The outside diameter of the connector is 4.5mm.

Connecting a simple vacuum gauge shows the negative pressure for each side. Use the idle adjustment screw to set for an equal value.