QuestionI recently purchased a 82 650 Highthawk that is in terrific shape exept for badly blocked carbs. It came with a spare , clean tank and another set of carbs. It lacked compression on # 3, so I removed the head and lapped all the valeves. This restored compression evenly across all 4. I totally disaaemble the carbs. (Keihin CV)and chemically cleaned them. The engine now starts first time, but will not run off choke. Off choke it will not run below 4000, and has a slight, interminant misfire. I can not seem to work out the logic of the idle circuts in the carbs, and have noticed that what I beleive to be the low speed jet is not drilled all the way through to the bowel. There are two jets , one is the main jet, and the other is next to it. As far as I can trace out it appears to be a air bleed only that runs from the intake throat, via the damper to the pilot screw.The jet appears to a emulsifier in that the one end has a center drillinf with 4 small holes through the sides, but the center hole does not go all the way through. I have read that by turning out the pioot srew this enrichens the mixture, but as far as I can see this would lean it as it does not seem to have any fuel running through it.
Hope I have made my problem clear,
Gus
AnswerGus, If you have properly cleaned the carb bodies and all open passages, the problem may not necessarily be with the carbs (!). Another consideration is that the extra carbs may or may not have the same parts/calibration as the ones that came on the bike. There are similar sets out there and some have different jetting or other calibrated parts. Check the carb bodies to see if there are some numbers/letters stamped on them, identifying the series and calibration. Looks like calibraton should be #35 and #118 according to the online microfiche service, though.
I sounds like that there may be a fuel flow problem which may or may not be coupled with an air leak. Honda, in their infinite wisdom, designed an automatic petcock system (fuel valve) that has a diaphragm, operated by a vaccum line coming from the carb rack. These diaphragms, along with the accelerator pump diaphragms will fail over time and usage.
I went to http://www.powersportspro.com/partsfish/login.asp and checked for some illustrations for your model and see that Honda doesn't sell parts for the $180 fuel valve! K&L has made a lot of replacement items, so have your dealer or shop check their catalogs for replacement spares that may work for your bike a much less $$$
Be sure that the petcock screen that is wedged up inside the fuel tank, in the petcock fitting, is clean and clear for maximum fuel flow and check over any fuel tank venting issues that can restrict fuel flow.
Idle mix screws are metering fuel flow and are not air corrections, so backing them out should richen the mixtures, if everything else is as it should be.
Bill Silver
