QuestionBill, thanks for the quick response. I have another question. Once the Honda cl125a motor starts, the engine revs to several thousand rpms without using the throttle. I have to use the choke to kill the motor before it blows up. The slide valve in the carb is not stuck and the carb has been rebuilt using a kit. Where would you start looking to fix the situation?
AnswerGary, first be sure that your throttle cable isn't hanging up internally or it isn't binding when you turn the handlebars. Back the horizontal idle speed screw all the way out, then turn it back into where it just starts to raise the slide, ever so slightly. The idle mixture screw is set at 1 1/8 turns out from gently seated in. That screw comes into the carburetor body on an angle. If you screw the idle speed screw all the way in and back it out 1 1/8 turns you will get a very fast idle.
Set float level at 21mm, with the float tang just contacting the needle tip, but not compressing the spring-loaded tip plunger. A very low float level will cause the engine to lean out and speed up somewhat.
Beyond the carburetor, I would ensure that the valves are adjusted, so that maximum compression is assured (125-150psi). Then, remove the point plate and check the mechanical spark advancer for sticking. Repair/lube as necessary, then set the maximum gap of the points to .012"-.016" and set them to open at the F mark alignment on the rotor/stator index mark. Spark timing will influence both engine idle speeds mixture settings.
Unless there are air leaks in the carb or at the carb to manifold area, the idle should be okay again. Suggested idle speed is about 1,000 rpms.
Bill Silver
