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Carb overflow?

Discussion in 'Maintenance and Servicing' started by MeltingDOg, Apr 22, 2012.

  1. Hi all,

    I have been having poor performance from my bike lately (low torque, increase in fuel consumption). I've been inspecting the carbs and one seems to leak fuel from the float bowl down the overflow tube.

    I've tried to do a bit of research online, but could anyone tell me what could be causing this and if it is contributing to the poor performance?

    Could it be the float valve not closing?

    Any advice would be awesome! Thanks!
  2. certainly the float needle jamming could be a cause. another possibility is a cracked float which sinks (which gives the same effect) but in both these cases you would have a constant fuel overflow unless you were really leaning on the throttle.
    persoanlly i'd find a service manual, study it til i could draw it in my sleep then rip the carbs off and have a good look, rather than just looking from the outside
  3. Float level is set ever so slightly high on the RHS carb. More trouble than it's worth to pull apart. That shouldn't be the problem. What do you mean by "poor performance"? How bad is it?
  4. Its an issue Ive posted about a couple of times already. Basically you must always hit power band to get any kind of power . That means I have to wind it up to over 3.5l RPM to take off from stop and I cant do hill starts. When cruising, the bike either has to be in our near powerband or else it slowly decelerates. Also coupled with this is poor economy - but I think that may be due to the fuel leaking out the overflow.

    I have replaced the plugs, checked the pilot screws and the throttle cables.... Just not sure what to do!
  5. I'd been having similar problems, Check your plugs if they're black sooty then your air fuel mix is incorrect running rich black and wet means oil fouling pull your carbies apart and let them soak in carby cleaner or another parts cleaner then blow out with compressed air, inspect your float assembly and enusre no minute holes in the floats, reassemble carby and check your float height again make sure that the floats move freely, inspecting the float needle valve goes into valve seat properly check for any crap and/or corruption and that the float needle is servicable, check your jets to make sure that they're secure and inspect your gaskets for wear, the older the gaskets get etc etc. Check your diaprhagm too for any holes or tears make sure that the gasket in is the groove correctly and place the chamber onto the carby making sure its well tight. If that fails take it to a mate who knows whats going on or a mechanic. Check you have the right size jets especially if an aftermarket exhaust is on. hope it helps
  6. That'd be my first guess, yes. Float valves do wear out over time. However, the most likely culprit would be a bit of debris stuck on the seat or the needle (that's the float valve needle, not the main carb needle). Or the float level could be too low, either by adjustment or due to a leak.