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CV34 Carburetor Connections

If you are installing Keihin CV34 carburetors, keep in mind that there are several types of assemblies.  The two main differences from a connection standpoint are:

1. Venting

2. Bowl drains

Venting - Some CV34 assemblies vent through the holes located on the intake venturi where the carburetor goes into the airbox rubber connectors.  The vent holes are connected by internal passageway to holes in the top of the bowl chamber.  Venting keeps the inside of the float chamber from developing a vacuum which would cause the floats to function erratically.  Some CV34 assemblies have black plastic tees connected between the 1 and 2 carburetors and 3 and 4. These tees serve the same function as the internal vent passageways connect to these instead of the holes on the venturi edge.  In either case, the vents must remain clear and unobstructed.  On some bikes, if there are vent tees, these will be connected to hoses which route to the airbox or may route over the swingarm.  The main idea is that they not be obstructed or pinched.  If your bike doesn't have the tees, don't worry about venting.  The point of the hoses is to route gasoline away from a hot engine in the event the bike overturns.  If it routes into the airbox, you will very likely need to replace your filter element if the bike overturns as it will be gas-fouled.

Drains - On the bottom of you float bowl you have drain nipples.  When you open the drain screw, the bowl will drain.  On SOME CV34 assemblies, there is a brass tube inside the bowl which is an overflow protector.  If too much gas enters the float bowl, it enters the overflow tube and exits the drain nipple.  Most CV34 assemblies do NOT have these tubes.  In the event that too much gas enters the bowl chamber, it will come out first the needle jet in the center of the floor of the venturi and flow into both the airbox and combustion chamber.  If even more gas floods the area, it will also come out the vents on the edge of the intake venturi and flood the airbox.  If you find gas in your airbox, it is a safe bet that you need to change your oil.  If you have overflows, the excess gas tends to run out the overflows and will be routed either into the airbox or over the swingarm.  If you have the brass tubes inside the float bowls, put hoses on the drain nipples and route them over the swingarm.  

FYI: The main reason that a CV34 will have a carburetor overflow is that the float level may not be set correctly or crud from the fuel tank goes through the fuel line and when it enters the float seat, it will not allow the float needle to shut.  The float needle/seat assembly are NOT gas shut offs so when the bike is parked, the petcock MUST work properly to shut off gas or you will likely have dribble from the #1 carburetor.

NOTE! Carburetors are numbered 1 to 4 from left to right as you sit on the bike!