Our frustrations with this led to a little experiment in which we replaced the stock carburetors with a set of Mikuni VM32 carburetors, as shown below:
You have probably heard of the Mikuni VM32 carburetor - it's a classic model used on a wide variety of small engines, and really popular for racing. It's extremely tuneable with a huge variety of adjustable needles, jets, etc, all of which are widely available.
Mikuni made many different variations on this carburetor for different applications. You may not have noticed, but there is something special about the ones we used. These were originally meant for 2-stroke snowmobiles and have small oil injection ports near the intake flange of each carburetor. We were able to convert these to be vacuum lines that can be used to synchronize the carburetors, which is very useful on any bike that doesn't have separate vacuum ports on the motor or intake manifold itself (think CB350, although you probably want to use a VM30 for the smaller motor).
The carburetor intake boots do need to be replaced to accomodate the Mikuni, but we were able to create a setup for the air boots that allowed us to use the original airbox. You will definitely want to experiment with the jet and needle sizes to get the correct fuel mixture at all throttle positions for your bike.
The only other real issue is that the choke levers, idle and mixture adjustment screws are usually "left-sided," so the right carburetor will be difficult to adjust. Right-sided carburetors exist, but are hard to find. However, there are different choke setups that can be installed, so once the initial carburetor setup is done, you can use the choke without much issue.
Also, we can do all this work for you if you're interested, just get in touch!
