1. You should not attempt to change the mixture proportions on any carburetor until you are assured that the rest of the engine is properly tuned . Changing the carburetor settings on an engine that has a problem elsewhere will only result in a subsequent loss of overall performance and perhaps engine damage. Carburetor adjustment should be the final step in a tune-up procedure.
Locating the Problem
2. The most difficult and most important part of any repair job is locating and correcting the actual problem and its cause. This is especially true in troubleshooting a carburetion problem, because the failure of many other parts of the machine will affect the carburetion.
For this reason, before attempting to regulate the carburetor, it must be determined that the air cleaner is clean and free of restrictions, the fuel tank has sufficient fuel, and the filter screens on the petcocks and carburetor fuel inlet banjo are not clogged.
The breather tube on the fuel tank must be checked for restrictions.
The spark plug must be of the proper type and heat range.
The ignition timing should be within the tolerances given in the specifications and all electrical connections must be clean and tight. All ignition components should be in good working order.
The crankshaft seals, head gasket, cylinder base gasket and engine center case gasket must be in good condition and the screws and nuts that secure these gaskets should be properly tightened.
The piston clearance must fall within the acceptable limits and the rings must not be worn enough to allow compression to leak past them.
The carburetor must be mounted to its manifold properly with no air leaks and the float bowl and internal fuel and air passages within the carburetor must be clean and free from restrictions.
Also, the exhaust system must be of a type designed for use with the
engine and cannot have any unnatural restrictions within it.
1. If, after checking the items mentioned in Section 1, Paragraph 2 of this chapter, you are reasonably sure that the problem is one of carburetion, you must determine whether the mixture proportions are too rich or too lean, and if this condition is present at one, several, or all throttle openings.
2. Run the motorcycle until the engine has warmed to operating temperature. On level ground or a slight uphill grade, with the machine in 2nd or 3rd gear, run the engine up to peak RPM by turning the twistgrip slowly, but smoothly, to full throttle. Then, slowly back the throttle off until it is fully closed. While you are doing this, listen carefully to the sounds made by the engine and exhaust.
3. If the engine makes a pinging or rattling sound, the mixture is too
lean. If the engine dies or loses RPM while you are opening the