Carb icing?

[california_rookie]

I had the privilege of riding an unfaired '84 Honda Goldwing the 200 miles home from San Francisco in near freezing temperatures today (2c) and was wondering if the low temperature and duration of the ride would have been enough to cause carb icing. I ask this because after a long ride, the bike would start to whistle a bit, as if something was catching the wind oddly. I doubt this was the case though, as it continued whistling a bit until I had almost come to a stop. Then it wouldn't do it again for quite some time.

I guess my specific question is, can carb icing occur at slightly above freezing temperatures if the ride is long enough? I was traveling between 70 and 80 miles an hour for about an hour both times it occurred. The bike ran completely fine other than that.

Thanks.
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[AcIdBuRnZ]

Sorry, can't answer you question here mate - interested in finding an answer to this myself!

But you think 2c is cold?
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[Kickstart]

Hi

Possible, but I would not think that was cold enough. Unless very cold I have only had carb icing when it is quite foggy.

All the best

Keith
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[skyline]

Hmm i know carb icing on my old 50cc could happen at higher temps than freezing but that was a 50cc with a tiny main jet. I doubt it was carb icing to be honest.

[jonboy]

It doesn't sound like carb icing - whistling is not really a symptom, bad running is.
It has happened to me at anything up to 5degreesC in the damp though, and that was on a 600. I think vapourisation of the petrol takes heat from the carbs and cooling them down to below ambient temperature like ice can form on a gas cylinder at room temp if it is emptied quickly. Or it might be the drop in pressure through the venturis that does it drops the temps as well.

[california_rookie]

Don't know what the hell it was, then. Just hoping there's nothing wrong with it as that'd kind of ruin the gift for my dad.

As always, thanks for your help.
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[Ninja]

The ambient temperature doesn't have to be freezing - just cold. It's the exta moisture in the air that tips the balance - as Kickstart noted, mainly when foggy and cold.

As fuel get vapourised and drawn into the motor, the vapourisation process draws heat out of the carb body (exactly the same process where your hands initially feel cold when you dry them with those hand blower dryers) This happens all the time but as the temperatures drop, this extra 'cooling' caused by the flow of fuel and air is enough to take the internal temperature below zero - sometimes significantly, despite the external temperature.
Air that is laden with moisture isn't 'good' on two counts - first, the presence of the moisture assists with the heat drawing process and second, there's enough moisture there to start literally forming ice.
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[california_rookie]

Well, my gloves were frosted a bit on the knuckles, so maybe the carb's got the same treatment. Would the fact that it's an unfaired flat four make it any more/less susceptible to this phenomenon? Also, would the beginning stages of this be accompanied by a slight whistle, or is there another explanation for that as well?
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[stinkwheel]

I don't think wings are noted for carb icing which would normally cause erratic running and intermittant loss of power.

Probably the wind howling through a hole in a plastic somewhere or induction noise.

Check for the source of the noise by pulling the clutch and killing the engine. If it is still whistling it is nothing to do with the engine.

Check your wheel bearings and the speedo drive cable, both of which can make odd noises if they are on the way out.
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[billy whizz]

Speaking from experiance here, carb icing can occur at any temperature below 6 deg. the main reason for this without going into scientific detail but imagine the wind chill you feel at 60 mph on your bike. Cold eh? Well what about 200mph? Thats about how fast the air moves through your venturi in your carb, now put some petrol on your arm and move it through the air or blow on it. Now you get the point, the evaporation of the petrol speeds up the cooling even more and depending on the amount of water in the fuel and in the air depends on how much ice you get.
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