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Ice on my carbies - what's going on?

Discussion in 'Technical and Troubleshooting Torque' started by Chairman, Sep 10, 2006.

  1. I'm not given to wild imagination, so just accept that this is not a joke...

    I discovered that there's no fuel filter on my bike, other than the coarse mesh on the standpipe. A quick snip of the line, in with a filter and I'm feeling much happier.

    On the way home from work (Thursday night) the bike misbehaves - it feels like fuel starvation so I pull over and, a minute later whetever was wrong fixed itself and I rode the last 2km home.

    Fast forward to today. Worried about why the bike died, and thinking I'd pinched a fuel line, I took of the tank and grabbed the fuel filter. Off fell a chunk of ice - yes - ice -as big as a 20c piece. It promptly melted on the garage floor.

    Now the bike has been in the shed, unused since Thursday and we haven't had any really cold nights here, so where the hell did the ice come from?
  2. Petrol always feels cold when you splash it on yourself when your fueling at the garage......

    {Any chance of meeting up this coming week, Mark??}
  3. The way I understand it is that fuel evaporates that’s why it feels cold its like sweet cooling you down that’s why when you get fuel on your hand it feels cold but when you put your hand in side the fuel it doesn’t.

    So I wouldn’t have a clue were the ice came from
  4. Carburettor ice has little to do with temperature in isolation, it occurs when air temperature gets to within 1 deg of dew point. In a carburettor it is caused by a combination of highly volatile fuel, high humidity and low ambient temperature. The extent of cooling, caused by the latent heat of the vaporised gasoline in the carburettor, can be as much as 20C. If this results in dropping below the dew point of the mixture, water will condense on the cooler carburettor surfaces, and will freeze. In highly humid conditions this can occur at surprisingly high temperatures. Aircraft engines have a carburettor heating system because of this issue, as ice blocking the main jet can stop the engine dead.
  5. u can figre this one out. if it happened, there's an explanation. some one could av put it in ur tank. you could have had an ice could drink when you changed the thing. OR a chemical reaction caused crystallizaition OR parts o ur bike is made from steel that draws heat away from the bike. was the ice clear or fuel colour?
  6. Carby ice sounds like the answer.


    See if you can decode the chart and fit that to the conditions you were riding around in.

    In laymans terms, as fuel vapourises in the carby it cools - sometimes enough to freeze water in the air. It would cool the outside of the carby too... but to the point of ice forming on the outside and lasting a few days???

    B and C model ZX9R's I think had a big issue with Carb ice. I don't know what you can do about it though. There's no "carb heat" button on a bike. [img:37:15:36e9dbb1af]http://users.pandora.be/eforum/emoticons4u/sad/533.gif[/img:36e9dbb1af]

    Just had another thought... would the pressure drop across the filter result in partial cooling???
  7. my guess...

    fuel is increasing the melting point for the water around it...

    just like salt decreases it.

    my fuel filter was leaking... came out to a near empty tank, and this "warm" ice it seemed, hanging off the filter...
  8. Yeah, right.

    "Tell us about the kayaks again, Uncle Mark..."

  9. Used to have the same problem with the Formula Vee on cold mornings at the track. First start, with the fuel laden air going down the inlet manifold at high speed, even with heat rising off the engine the manifold was ice cold to the touch. Hit the track like that and the car would misfire like a pig.

    Solution was to let the engine run for a while, turn it off and let heat soak do its trick, the carb and manifold absorbed heat from the block and ran fine from then on.

    Dunno if that helps, but I thought I'd share anyhow! :grin:
  10. The ice must have came from his J.D. and coke, in a drunken stupor while he realised that ice does not belong in J.D.


    Where the hell did you fit your LPG tank on the bike?


    check that you are still anatomicaly correct still, did you freeze one of your balls off?
  11. I'd say, what is happening is, there is a mechanical restriction in your new filter.

    The mechanics of the fuel going through the restriction is causing the fuel to evaporate. When it evaporates it is an endothermic reaction (gets cold). This cause ice to form on the outside, and possible inside, of the filter.

    This is the same way a fridge or air conditioner works. Pump a liquid through an orifice, to cause an endothermic reaction.

    So you have been starving your engine.

    Find a better flowing filter ASAP as running lean like this can cause serious damage to your engine.
  12. You're too :cool: for school, Chairman.

    {Speaking of which I shall be catching up with Major Allen (Yes, you laddy! :evil: ) at the Naval and Military Club in short order.Tally Ho!}
  13. Incitatus has it right. Planes have carb heat for this very purpose and I have experienced ice formation in carbs on a plane at 28 deg C. It would explain why your bike was running rough and also why it ran again after you stopped. Ice can form inside the carb and block fuel flow and be stopped completely in a bad case.

    Not something I have heard about in bikes too much but on planes it is a common occurrence (well if you don't use carb heat it is!!!).
  14. ibast got it right. robsalvv saw a flicker of light as well.

    If the ice formed on the outside of the filter, which it sounds like it did, it's water ice formed from water condensed out of the air. Was it on the downstream side of the filter? If so, you have a pressure drop across the filter. Hence, the petrol is evaporating in the line past the filter, or inside the filter as it passes through. Evaporation is an endothermic reaction. The petrol evaporates at the lower pressure provided by the engine on the downstream side of the filter, and "steals" heat from the surroundings to enable the petrol to remain in the vapour state. This cools the back end of the filter. The petrol is working just like coolant in a refrigerator.

    This explains the "starving" of the engine as well. Hmmm, more than likely would result in a lean burn. Your plugs should tell you if it is.

    There probably wouldn't be any ice inside the fuel line or filter, as there shouldn't be any water in there, or air carrying water vapour. The petrol isn't going to freeze unless it gets really really cold.

    So much for the new filter idea. Is it fitted back to front? Most filters are supposed to allow flow only in one direction, and restrict back flow. Should be an arrow on it. . .

    Spongesam, your leaking fuel filter could also have had an endothermic reaction as the fuel exited the hole and expanded. The cooling would have cooled the filter and frozen water vapour in the air.
  15. Good point. didn't think of that one.

  16. It does indeed occur on bikes, and the longer the inlet tract, the more likely it is. It was so bad on the 906 Paso, that Ducati released a carb heater kit.
  17. What does it say about BMW riders when the seat warmer comes standard?

  18. Ah, but you did remember the correct name for a reaction that absorbs heat, which I then used without compunction. Hmmm, Endothermic. Thermodynamics 101. Amazing how much you forget. :shock:

    Of course, we are both on the wrong track if the ice was actually on the carbs near the jets or throat, where the heat is absorbed. Would be funny if it started just after fitting a fuel filter though.
  19. Whatever it says, it doesn't say it for me, neither of my BMWs have seat warmers... :p :p
  20. ...if Chairman installed the filter back to front... I'll go heave...