Honda CL / CB350 Carburetor Rebuild Guide Part 2: Emulsifier Assembly, Float Height Adjustment & Jet / Float Bowl Installation

Posted by Brenden on 4/25/2017 to CB350 / CL350 / SL350

In part two of our Honda CL / CB350 carburetor rebuild series we begin putting everything together. In the following rebuild videos, we assume that the carburetor body and any other parts that are being reused have been thoroughly cleaned inside and out. Many folks think that a rebuild involves taking the carbs apart, replacing the parts and putting it all back together; this is not thorough enough. All the passageways, parts, crevices and mechanical pieces need to be super clean, like clean enough to eat off of. No dirt, varnish, goo, corrosion, rust or any other debris that will inhibit fuel or air flow. We do have a particular sequence in which we like to assemble the carburetor, starting in the float chamber then working up to the diaphragm area.

Emulsifier, Idle Jet and Float Needle Seat Installation: The first step in rebuilding the Honda CL / CB350 Carburetor is to install the emulsifier tubes as well as the idle jet (aka pilot jet) and float needle seat. These are all the deep internal parts located in between the float bowl and the venturi (middle of the airflow passage). There are two emulsifier tubes (primary and secondary) which must be pressed into place, a dab of light oil will help with this. The idle jet is very small and is installed with a flathead screwdriver then covered with a tiny rubber passage plug. This is also a commonly missing part in the carburetors but is included in the Honda CL / CB350 carburetor rebuild kit. The float needle seat needs to be pressed into place and secured with the retaining clip. Upon looking at the float needle you will see a tapered pointed end and a spring loaded pin at the other. The pointed end goes in the needle seat, while the pin makes contact with the float. It is this spring loaded pin that will have an effect on float height, which must be checked when installing a new float seat and needle.

Float Height Adjustment & Bowl Assembly: This is a critical part for the Honda CL / CB350 Carburetor rebuild. There is a good bit of misinformation out there in regards to the float height specification. The early style Honda CL / CB350 Carburetors used a square or “bread loaf” type float. However, the mid and late style Honda CL / CB350 Carburetors use a round float design; which is what we will be setting on this specific rebuild. The original Honda service manual published the height specification for the early square but was never updated for the round style float which happens to be the float used in the vast majority of the carbs. 

The float height specs are:

You will need a something to measure the float height with; we prefer to use a caliper; however, a precision ruler with a MM scale will work as well. The adjustment process takes a little trial and error and changes must be handled gently as the float is a delicate piece. Also the float height must be checked on both floats as there can be a variation in height if the hangar (piece that connects the floats) is warped. Once the float height is set then the main and secondary jets can be installed. The trick to getting these in is to first place them in the retainer (funky spring thing) and then push the pair of jets into place. A drop of light oil on the O-rings will help them seat in place. Finally the float bowl can be installed.

A few tips on getting this put into place:

  • Use some Vaseline or white grease and put some in the groove of the float bowl as it will hold the sealing O-ring into place.
  • Give the bowl O-ring a light stretch and stick it in the bowl.
  • The bowl must be installed just perfectly as there is an overflow tube in the bowl that has to pass through a small hole in the jet retainer. Sitting the bowl on the carb body it will be raised up about 1/8” because the jet retainer has not been compressed. It is the bowl pressing on the retainer that keeps the jets securely in place.
  • I like to use a dab of anti-seize compound on the float bowl screws so removal in the future is easy.
Finally there are two styles of drain plugs used on the Honda CL / CB350 Carburetors; early style has a small head (about 8mm in diameter) and seals with a aluminum washer. The late style drain plug has a large head (about 12mm in diameter) and seals using an O-ring. If you have not noticed there are small passages drilled in the drain plug to allow draining of the float bowls without having to remove the whole screw. Check to see if they are plugged as the are often packed with dirt. A small drill bit and wire will help get them cleaned out.


In part 3 of our rebuild series we will install the slide with diaphragm and test for proper operation.

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