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Fixing carb flooding - advice...

Discussion in 'Technical and Troubleshooting Torque' started by mattb, Aug 15, 2007.

  1. I've never opened up a carburettor before, and I suspect, judging from various forum's posts, for instance
    that I need to clean out any dirt from the needle and seat, but I have no idea how to do this - not the first clue. Can anybody explain what I should be looking at, and how to do it (I heard mention somewhere in the past of a spray to do this with).

    It's my partner's SR185. It's been sitting for a while, and while sitting it just suddenly started flooding at the carb - not dripping, I mean fuel gushing out of the overflow tube! The bike wouldn't start. I drained the carb, and got the bike going and rode around, but as soon as I stopped, it wouldn't start again. I took the float bowl off with the carb still attached, looked at it through uncomprehending eyes, put it back on, and got the bike going again, and rode it run until I stopped and then it wouldn't start again. I'm wondering if there's some crap in there and I'm knocking it out each time, which would also explain the flooding?

    Also, it had trouble idling, and would ride fine at higher rpm, but would want to stall when I came to a stop. I turned the pilot screw up and it increased in revs, but then rapidly decreased to the point of dying out. The top of the (old) spark plug (not the sparking end, for I can't get it out of the bike at the moment) was seemingly damp.


  2. Matt,

    needle and seat is a pretty low tech set up.

    Where the fuel line feeds into the bowl there will be a tapered brass (probably) "seat" on the inside top of the bowl. The "needle" fits into the seat and is controlled by the float which sits inside the bowl. As the fuel level in the bowl rises the float pushes the needle into the seat and blocks the flow of fuel into the bowl.

    Simple as it is plenty can go wrong.
    - damage/wear/crud interferes with the needle's ability to block the fuel flow
    - floats can crack or get holed meaning they don't float on the fuel anymore and so don't push the needle into the seat.
    - there's usually a little tang on the float to push the needle, these can break off, again no chance for the needle to block the fuel.

    A little common sense will tell you where the problem is.