Carburetor frosting

LeeinIL · Mar 13, 2016

Why is it a carburetor on one tractor will frost up when it is running and another one doing the same job wont. I have an 806 that is horrible about frosting and condensation. I ran another 806, same day and same job without so much as a drop. One of my customers has an 830 Case and he has asked me why it does that. Is there an air leak somewhere in the casting that is not causing an issue with it running but making it frost up? I really don't like telling him, we'll it runs fine doesn't it. Thanks, Lee

JD Seller · Mar 13, 2016

It is frosting up because the carburetor is cold from evaporating the liquid gasoline. Different tractor models and different carburetor models are effected differently by cold weather. Some never frost up and others do. It is complicated to figure out why two identical tractors may act different. One variable is the condition of the motor. While they maybe the same model with the same carburetor, the motor maybe worn more on one than the other. The one not frosting actually could be in worse shape. Less vacuum through the carburetor would make it frost up less. So worn out engine may not frost.

FBH44 · Mar 13, 2016

I thought also it has to do with the air flow accelerating through the venturi. The rapid increase in speed causes both a vacuum that draws in gasoline at that throat, and it also drops temperature. I think. The venturi cools down, the body of the carb cools down, and if the outside ambient air has enough moisture, the moisture can condense and form frost.

old · Mar 13, 2016

ALL carbs do that just some due to things they have changed do it worst then others. Think about all those older cars that had a tube going form the exhaust manifold up to the air intake. That was there to stop carb icing. When gas is atomized in the carb it causes things to get very cold which in turn causes the icing. Or in other words that is how carb works

RandyB(MI) · Mar 13, 2016

It is a combination of the two but is more about the air speed. In the case of a supplied air respirator in a paint shop , we have a little apparatus that fits on our belt that is nothing but a series of "venturi,s and air diverters to speed up the air flow from the supply unit. The supply unit probably is set at around 7-10 psi to supply the hood. We use these in the hot summer and the air from them to the hood will almost freeze your face if you adjust it that way. The unit itself will be covered with frost so we have it in a leather case so it can't touch ones skin. There is NO evaporating fuel or chemicals involved. Rpm of tractor , position of sun and/or wind and condition of air filtration could all explain two equal tractors being different. There are no two equal tractors/conditions.

cool hand · Mar 13, 2016

I believe (IIRC!!) a difference in the carburetor adjustment/settings can make a difference in the likelihood of frosting.

ss55 · Mar 13, 2016

3010-4020 gas Deeres had manual "heat valve blocks" that had to be turned to heat the intake manifold during cold weather. Many 1950's to 1980's vehicles had "thermostat heat valves" operated by a bi-metal flat coiled spring. I think some six cylinder IH gas tractors also used a thermostat spring to control a heat valve. If your tractor has one, could the valve stuck?

jacksun65 · Mar 13, 2016

Has to do with humidity and high pressure to low pressure. When a high pressure gas goes to a low pressure it absorbs heat. Just as when you compress a gas it gets hot. like in a air compressor.

D beatty · Mar 13, 2016

I had the same trouble with Farmall B and built jacket around muffler with a tube to air cleaner stack. Put it on in fall and remove it in the spring. You wouldn't believe how much better engine runs in cold weather.

JOCCO · Mar 13, 2016

Others have said what causes it and some areas and weather patters are pretty bad for it. It can shut an engine down or make it run poor. There was a type of heat tape for it years ago then some had factory manifold devices to heat the carb otherwise we used to make a heat pipe. I still se it a few days a year if weather is just right.

Geo-TH,In · Mar 13, 2016

Here is a previous link I posted earlier this year. What you have is a common problem certain times of the year when humidity and temperature are just right.
Previous post covering carb frosting

teddy52food · Mar 13, 2016

The one that is frosting up is doing a better job of breaking down the gas & mixing it with air. In other words, more efficient.

rustred · Mar 14, 2016

perfectly normal. as this is called the "venturi effect". the air is speeded up as it passes throught the venturi causing it to cool down. once the engine warms up the frost goes away.

gab · Mar 14, 2016

My Super C did that for about 10 years, also ran rough until it warmed up. Always had problems with the Carter carb. any way and replaced it with a new Zenith. The manifold above the carb. still gets frosty but it runs fine now, think the new one is more efficient atomizing fuel.

Carburetor frosting

LeeinIL

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JD Seller

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FBH44

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old

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RandyB(MI)

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cool hand

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ss55

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jacksun65

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D beatty

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JOCCO

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Geo-TH,In

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teddy52food

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rustred

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gab

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