How to rebuild the factory Keihin CV carburetors on your Honda CB350 / CL350 / SL350 K0

Attacking and cleaning the factory CV carburetors on your vintage Honda is a right of passage in ownership of these motorcycles. Gas degrades within 6 - 12 weeks(modern ethanol gas even quicker), causing the jets to be clogged and warranting dry/old o-rings in need of replacement. Even the worst of the stock carburetors can usually be repaired with a full carburetor rebuild kit, and possibly new floats and diaphragms.

Before starting the rebuild, be sure reference our CB350 carburetor identification article to know whether your CB350, CL350, or SL350K0 is using early, mid, or late style carburetors.

Honda CB350 Carburetor Identification Guide

Part 1: Disassembly and identification.

Learn the step by step process on how to disassemble the factory Keihin carbs found on Honda CL / CB350K and SL350 K0 series motorcycles. The tear down includes how to remove and identify jets, emulsifier tubes, floats, mixture screw, slide and diaphragm. The carbs must be taken apart to this level so that the body and small parts can be properly cleaned and ready for rebuilding.

Part 2: Pilot jet, float seat, and emulsifier tubes installation.

Once everything is throughly clean, the reassembly starts with the float bowl area of the carb. We show you how to install the emulsifier tubes, pilot jet and float needle & seat for the original Keihin carburetors used on Honda CL / CB350K series motorcycles.

Part 3:

Setting float height, installing the jets, and sealing the float bowl.

In part three of our Honda CL / CB350 carburetor rebuild series the focus is on setting the float height and installing the main & secondary jets. We button the carb up by installing the float bowl with a new o-ring gasket and drain plug. This covers most of the carburetors used on Honda CL / CB350K series motorcycles, however early versions as well as SL350 slide carbs have a slightly different float height setting.

Float height can vary on the high end at 23mm and low end at 26mm.

The height will vary based on float needle spring back force and the condition of the floats and hanger.

Part 4: Slide assembly, diaphragm inspection, and installation.

Learn how the vacuum slide is assembled and how to inspect the diaphragm for any tears, rips or blemishes to finally install and seal up the slide / diaphragm and finish the top side of this Keihin CV carburetor used on Honda CL / CB350K series motorcycles.

Part 5: Mixture screw installation and diaphragm test.

Things are wrapped up by installing the idle mixture screw and setting it for initial start up. Finally we show you how to test the slide & diaphragm for proper operation; this is critical inspection on any CV or constant velocity style carburetor like the Keihin carbs used on Honda CL / CB350K from the factory.

Before reinstalling the carburetors on your CB350 / CL350 / SL350 K0 be sure to read our article about how to bench synch and on bike synching so your motorcycle will run properly.

How to Synchronize Carburetors Honda CB350 / CL350 / SL350K0