About Rich Johnston Expertise I have honda repair experience on all vintage Hondas from 1972 through 1980. I worked in a Honda dealership while going to college and have experience in all types of honda motorcyle repair. I don't have any experience on other brands.
Experience
Education/Credentials BS degree in mechanical engineering, Honda technical school graduate of 1975
Question I bought a 1993 cb 750 nighthawk on line with the carbs in a box along with some other parts to finish the assembly. I have thoroughtly cleaned the carbs 3 times now and still cannot get the engine to run without the choke on a small amount, it seem like the low speed jets are plugged but they are not and all the passage ways are open and I can blow through them easily. It idles OK with the choke slightly on, when I turn the choke off the idle dies down to under about 600 rpm but seems strange that the idle screw when I turn it does not do anything to the RPM level up or down???? OK with that said if I turn the throttle it dies so I have to use the choke to get the rpms up. The initial transition between idle and giving it some throttle makes it die. I am puzzled and I have rebuilt carbs before but have had great success. Could this need the carbs synced, I have purchased Carb sync unit from Motion Pro and have not tried this yet. I appreciate your help
Answer Kim, the problem is still a lean air fuel ratio at idle and just off idle. If the jets and passages are clear as you indicate, the only other thing that would cause this is a low float level. My experience is on older pre-82 Hondas so I can't tell you how to check or set those floats. As long as I've convinced myself that the carbs were clean and there wasn't so air leak somewhere, I'd try raising the float level a mm or two and see if it doesn't fix the problem. On older VF carbs, setting the floats correctly was pretty trick and easy to get wrong.
