QuestionBill, I've had this bike since 1964. During the late 60's I was living in Denver. I had been in Minneapolis when I bought the bike. The engine started to foul plugs while at the Denver elevation. I remember changing jets in the carbs. I now live in Raleigh NC. The bike does not start or run well. When it does run, it will be for only a minute or two, then one pluge fouls out. I can trade plugs side to side, the foluled pluge will "clean" it self and the same cylinder will foul the plug from the other cylinder. What should the jet sizes be? What is the drill size of the jet hole, I have machines that I can accuratly drill the jets. What are the other specs for the carbs?
AnswerRon, Oh, great! Finally a question on Vintage Hondas! :>)
I have written extensively on the Super Hawks and have owned several, including the CYP77 Police bike on the top of my website.
I lived in NM when I had the CYP77 and had to drop the main jets from 135 to 125 and drop the needles a notch or so, as well.
Stock specs: 135 mains (sea level), #42 idle jets, needles set with clip on the 4th notch from the top and float level at 22.5mm.
Bear in mind that the carbs have to be absolutely clean inside, including all passageways for fuel and air. I had a CB77 that fouled the plug on one side and the air bleed passage to the main jet circuit (in the carb throat) was plugged!
Before you start adjusting the carbs, be sure that the ignition timing is set correctly. There is a problem with getting the spark timing accurate on both sides at idle and at full advance. The point cam gets loose in the camshaft and the timing wobbles all over the place. When both sides are set for maximum advance, the idle timing will be 5 to 10 degrees different, side to side. We developed an electronic ignition for these bikes to fix that issue. If the timing is out too much or the advance springs are weak, causing the spark timing to start too early, it will be impossible to get the bike to idle properly, as the two sides will always be out of phase with each other. Timing affects the manifold vacuum, which causes changes in metering.
Keihin jets are metric, of course, but basically you can multiply .039 or so. by the number to get the diameter in inches. #42 = .016" for the idle circuit. .052" for the main jet. Better to clean them with a strand of copper wire, if possible, rather than to run a drill bit down inside, scratching the surface.
Be aware that the carb slides are L and R! If you switch them, the idle will be very poor and the plugs will load up very quickly. Cutaways go towards the air filters!
Nice to hear from an original owner of a CB77!
Bill Silver
www.vintagehonda.com
