Motorcycle carburetors can easily be restored to working order if gunked up with varnish or dirty fuel trash. Constant velocity, mechanical slide and fixed venturi carburetors all can be removed, cleaned and rebuilt by the layman, using a few common tools and the proper rebuild kit for the make and model of the vehicle. Procedures for setting float height and synchronizing the carburetors (if multiple) may come with the rebuild kit or may be obtained from an OEM service manual.
Take note of all the linkages going to the carburetors and carefully remove them. Take some pictures before disassembly begins. Remove the mounting bolts on the carburetors and remove the carburetor assembly from the engine. Stuff a clean, lint-free rag into each intake port to prevent foreign solids from entering the engine if the intake manifold gasket material does not cleanly separate from the engine. Scrape the gasket material off the engine and carburetors or manifold, taking care not to damage the machined gasket surfaces.
Remove the drain screws and drain the float bowls. Remove the float bowl screws and pull the bowl off. The parts should be perfectly interchangeable if dealing with a multi-carb bank, but it is still a good idea to keep each carburetor's parts together and segregated from the others. Carefully remove the bowl gasket. Gasket surfaces will be aluminum most likely, and easily damaged by steel tools. Remove the float pin and the float/needle assembly should come free. Remove all of the jets that are accessible from here.
Constant Velocity (CV) carbs and mechanical slide carbs must have their to caps removed. Remove the cap screws from the carb and extract the slide. Be most careful with the slide on a CV carb, as it will have a thin rubber diaphragm that is easily damaged. If this diaphragm gets damaged it cannot be repaired, only replaced. Carbs are now disassembled as far as you should take them.
Clean the carburetors with an aerosol-propelled cleaner in a can with a straw. The straw is useful for reaching into nooks and applying focused direct pressure. The cleaner will dissolve any varnish and displace any water in the carburetors. Wear safety glasses and use in a well-ventilated area, as the cleaner is quite noxious and extremely volatile and flammable. Shoot cleaner into all air passages, jet tubes, jets and orifices. Use sufficient cleaner to dissolve and flush any foreign substances away. Visually inspect the carburetors and the components for signs of wear or damage. Shake dry or carefully blow dry with compressed air. Be sure the carburetor is completely dry and free of solvents before you begin reassembly.
Reassembly is the reverse of disassembly, with the addition of replacing all gaskets included in the rebuilt kit and the float needle--as well as checking bowl-float height. Bowl-float height procedures vary widely between makes and models, so it is recommended that you reference your OEM service manual for the procedure.
