Motorcycle Repair: 81 honda cb650 carb kit needle and seat, honda cb650, vacuum source

Question
We have an 81 honda cb650 with the cv carbs, and we purchaced it after it sat for 3 years. The carbs keep overfilling with fuel, and leaks out up high in the carbs. We tried cleaning the seats for the needles, and the needles do not look worn, but it still leaks. We tried to order carb kits which says the seats are included, but they are not. Seats are pressed into carb body, and not screwed in. We are wondering if there are any kits that includes the seat for this carb, or any information with this problem. also in the carb kits that we purchaced there are small jets that I do not see in the carbs that will screw out. Thanks for any help. Paul

Answer
Paul, the 1979-80 carbs were a different design and perhaps you have gotten kits/parts for the earlier slide-type carbs.

Being that the seats are pressed into the carb bodies, kits won't come with them as removal and installation would be very difficult. Seldom do the seats get damaged, unless there is old fuel varnish and acids working on them for a long time. The viton tipped needles are generally pretty tolerant of seat irregularities, in most cases.

If all four carbs are flooding at the same time, high up in the throats, rather than from the overflow tubes (or in addition to), my experience has been that the carb float bowl venting system passsages in the roof of the float bowl are clogged/blocked. I don't know if you pulled the whole carb rack and disassembled everything or just pulled the bowls to clean the jets, etc., but you may want to look at the venting passages and any associated hoses. For carbs with the automatic fuel shutoff valve, be sure that you are hooking the right vacuum hose to the valve assy from the carburetor intake vacuum source.

One other thing that happens on these carbs, when they are cleaned and installed, is that the floats often drop down too far, causing the needles to get cocked and jammed and causing flooding. You have to get the engine started, shut off the petcock while it is running and then tap on the carb bodies with a plastic mallet or screwdriver handle, to help seat the float valves again. Rocking the bike back and forth may help, as well.

Bill Silver