I drove to work in my kit this morning, a chilly 10 degs C but the sun was out. After 5 mins driving, I seems to lose some power and it runs rough at low revs, if I boot it, the power comes back. This happens for 1-2 minutes then everything is normal. It allways seems to happen on cold mornings after 5 mins driving.

Is this carb icing?? Or something else?
How can I prevent it?

I have 1.8 Zetec with ZZR carbs + pipercross filter.

[Edited on 25/8/09 by Slater]

seems a wee bit warm for carb icing, I usually hit problems below 7 degs, but then that is using ordinary car carbs. If you turn it of, give it a few minutes then restart and it’s back to normal then it’s usually carb icing to blame. Bike carbs are quite vulnerable to it due to the usual hose between them and the manifold preventing any heat getting up from the cylinder head and melting the ice

[Edited on 25/8/09 by Mr Whippy]

I've got a similar set up - Zetec with ZX6r carbs and pipercross filter, and have no problems with this even driving when its below freezing.

Does your air filter stick out of the bonnet? Mine is completely enclosed so maybe that makes a difference.

I've just looked in your archive and your carbs are much further away from the head than mine so that probably accounts for the difference.

[Edited on 25/8/09 by whitestu]

Carb icing isn't a problem when the temp drops to below zero, below that and there's no moisture in the air to cause problems. It usually manifests itself a few degrees above freezing.

quote:

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Originally posted by UncleFista
Carb icing isn't a problem when the temp drops to below zero, below that and there's no moisture in the air to cause problems. It usually manifests itself a few degrees above freezing.

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remember how the old mini used to have a thing that directed air from around the exhaust manifold into the carb air intake?
could you make up something like that? even just to blow some warm air over them?

This may help - it's talking about aircraft, but it's also relevant to cars:

LINK

The most significant line, after listing the causes, is "In other words, carbureted engines are susceptible to icing almost anytime"

In your case, low temperature and high humidity can cause it. My bike carbs used to have a connection to the coolant plumbing to keep the venturis warm, but that vanished when I respaced them.

While Googling I found this picture:



The accident report listed contributing factors as: "weather conditions conducive to carburetor icing, unsuitable terrain available on which to make a forced landing and the tree."

[Edited on 25/8/09 by David Jenkins]

Have you connected the carb heater pipes?

i have mine heated, there are little pipes at the bottom of my carbs and i have piped them in my cooling system

stuart