carb iceing

Discussion in 'Sportster Models' started by kennyw, Nov 29, 2010.

  1. kennyw

    kennyw Active Member

    hi having a few problems with what i've been told is carb iceing up,use bike for work last week on nights,parked in bike shed temps went down to -3 & colder with wind chill,at 6;30 bike started ok with full choke warmed her up.choke in and off i went home,few miles lated when i throttled of engine almost cut out had to give it a few revs,and that kept happening all the way home,i started to use the winter fuel treatment,is it to cold for a harley ?we are expecting -15 ,so is it tme to wrap her up for the winter?
  2. karlsbike

    karlsbike Active Member

    I've had similar symptoms - poor running, had to keep reving it so it didn't stall. As I am sure I had no leaks or any other issues, I concluded with carb icing (Stock CV40).
    This can (and did for me) happen at plus degrees (C, i.e. above freezing) as the venturi effect causes higher air speed = lower temp than ambient.
    I'm a chicken; -10C her for the past week or so, and she is already torn down for major overhaul;).
  3. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    I have had a fair bit of carb icing in the past temperature needs to be warm enough so that the moisture in the air is not frozen then due to the chilling effect of the fuel vaporisation the moisture in the air freezes and blocks some of the jets
    can get the carb icing here from about +3 to +15 centigrade but it depends on the moisture content in the air at the time
    silkolene pro fst was developed by silkolene at the request of kawasaki uk to develop a product that would reduce the carb icing problem suffered by some kawasaki models fitted with keihin carbs
    Fuchs Silkolene Powersports Oils & Lubricants
    i replaced the carbs on my 2 big twins with mikuni hsr 42 they seem to be a lot better in our damp conditions

  4. dbinbc

    dbinbc Active Member

    fin 676 is correct, carb icing will only occur when there is liquid water vapour in the air. Below freezing that vapour is micro ice crystals that will just blow right on through. Icing takes place when the dew point is very close to the ambient air temp and the ventury effect drops the air temp below the dew point. If you are riding below the freezing point. Something that could be happening is that the very cold dense air is creating a change in your fuel mixture.