carburetor icing

[D B Cooper]

Was cutting up branches and bucking today . 30 deg. and snowing, saws started acting up,pulled air cleaner cover seen carb covered in frost. Ms 180 for the branches ,Had the worst icing with the wt 215 carb.
No shutter for air box heating. 362 M-tron started acting up ,took a look at the carb it was all frostie then I moved the shutter to winter mode then it behaved.
first time I ever had this happen.

 

[Clemsonfor]

Was cutting up branches and bucking today . 30 deg. and snowing, saws started acting up,pulled air cleaner cover seen carb covered in frost. Ms 180 for the branches ,Had the worst icing with the wt 215 carb.
No shutter for air box heating. 362 M-tron started acting up ,took a look at the carb it was all frostie then I moved the shutter to winter mode then it behaved.
first time I ever had this happen.

Sounds like it did what it was suppose too once the shutter was in the right position.

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[pro94lt]

Icing at 30???

 

[63expert]

 

[angelo c]

You dont know "icing" until you're at 3000 ft in a Cessna 150 over water and you start pulling your carb heat...and hear the engine shake and shutter...then pop.....and clear out.... yup....you start to get very religious fast.

 

[merc_man]

Icing at 30???

My thought too. I have cut in -30°c with no icing up.

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[Dub11]

If you got enough humidity in the air it can happen at above freezing temperatures. We use some air mixers at work and the mufflers on them will freeze up after 20 mins. It's never below 85 in that building.
https://en.m.wikipedia.org/wiki/Carburetor_icing

 

[huskyboy]

My thought too. I have cut in -30°c with no icing up.

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Probably because his were schteels. Lol

 

[Brush Ape]

I've heard of icing on the cake but not icing on the carb,...

Two thang, get ethanol free, close you winter shutter, run a Stihl they are factory hot. OK that's three but you homos can't spell or count so two outta three ain't bad...

 

[Al Smith]

The only time I ever saw this was on a sprint car over 50 years with a punched out 392 hemi with 3 giant Bendex,-Strombergs running alkie .It was 80 degrees out

 

[mels]

marvel-shebler updraft carbs on these old tractors frost up nicely at 45~50 degrees

 

[Bigmac]

I have had my alcohol banshee carbs frost up on the outside at 50 plus degrees, also had them sweat a lot when it was in the 60’s!

 

[Backtroller]

To avoid icing, Here’s what I did on my snowblower repower. It had a snow king Tecumseh. Now it runs a Honda knockoff. I made a cross over pipe and bought an adjustable high speed jet. It runs very nice and idles much better than the snowking. Smaller motor but it’s OHV and runs at a higher rpm. Powerwise it’s on par with the old 8hp.

 

[angelo c]

marvel-shebler updraft carbs on these old tractors frost up nicely at 45~50 degrees

Same carb on the C150 ...
same Magnetos as well...
kinda scary eh

 

[Basher]

Air cooled Volkswagon carb would freeze solid white even during the summer if the heat riser pipes were disconnected or even if the gaskets between the risers and air inlet were missing. Summer or winter they would run fine if the risers were connected properly.

 

[stihl_head1982]

I've heard of icing on the cake but not icing on the carb,...

Two thang, get ethanol free, close you winter shutter, run a Stihl they are factory hot. OK that's three but you homos can't spell or count so two outta three ain't bad...

 

[stihl_head1982]

 

[heimannm]

As the air moves through the venturi the pressure is reduced, that is why/how the fuel moves from the wet side of the metering circuit into the carburetor. The change in pressure combined with the evaporation of the fuel removes a lot of heat resulting in the icing.

The mufflers on the air motor are the point where the high pressure air escapes to the atmosphere (lower pressure) and the change in pressure removes heat, more air removes more heat and the icing is a result. You can see the same effect when you remove a valve stem from a tire and hold it in the air stream as the tire empties. Again, the air changing from high pressure to low pressure absorbs a lot of heat...if you do it just right you can see ice forming on the valve stem.

All air conditioning systems work on the same principle, the compressor produces a relatively high pressure liquid (refrigerant) and as it passes through the evaporator it loses pressure and vaporizes removing heat in the process.

As the chart shows, the right combination of temperature and humidity can produce icing results even above freezing temperatures since the operation of the carburetor produces the right conditions (high to low pressure and the evaporation of a liquid) to remove a lot of heat.

After all that, I have never had that experience myself either in a plane (as a passenger) or with a saw. My 1966 V.W. Beetle was much more likely to suffer from vapor lock that carburetor icing.

Mark

 

[Clemsonfor]

As the air moves through the venturi the pressure is reduced, that is why/how the fuel moves from the wet side of the metering circuit into the carburetor. The change in pressure combined with the evaporation of the fuel removes a lot of heat resulting in the icing.

The mufflers on the air motor are the point where the high pressure air escapes to the atmosphere (lower pressure) and the change in pressure removes heat, more air removes more heat and the icing is a result. You can see the same effect when you remove a valve stem from a tire and hold it in the air stream as the tire empties. Again, the air changing from high pressure to low pressure absorbs a lot of heat...if you do it just right you can see ice forming on the valve stem.

All air conditioning systems work on the same principle, the compressor produces a relatively high pressure liquid (refrigerant) and as it passes through the evaporator it loses pressure and vaporizes removing heat in the process.

As the chart shows, the right combination of temperature and humidity can produce icing results even above freezing temperatures since the operation of the carburetor produces the right conditions (high to low pressure and the evaporation of a liquid) to remove a lot of heat.

After all that, I have never had that experience myself either in a plane (as a passenger) or with a saw. My 1966 V.W. Beetle was much more likely to suffer from vapor lock that carburetor icing.

Mark

I can see ice where my compressor drain valve hits the concrete below it. It's about an inche or so from the concrete. It will form ice at certain times on the concrete even in the summer here in the south. In the winter it will alms make a reverse ice cycle all the way back up to the valve.

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[jockeydeuce]

I have experienced this numerous times...Always exactly the conditions the OP described. Right around freezing with high humidity. Stihls are the absolute worst for this. I seldom if ever have it happen with any of my Husqvarnas, but my 044 and 064 are terrible for it.