Natural gas doesn't liquifie at normal temps and pressures, and since it is not supplied from a tank, none of the above LP problems apply to NG.
Carb ice is caused by the moisture in the air freezing when the air pressure drops in the carb, so will happen with any fuel that is carb'd. Carb ice is more of a problem from around 32 deg F to the 6o deg F and air hold more moisture at those temps.
So oil viscosity will be an issue just like any engine as will cranking speed. You'll need enough vacuum to open the regulator, but there should be no special running problems.
NG pressure supplied by the pipeline doesn't drop with temp, it is a constant.
As to mixture, the colder the air the more dense, so as with any carb's fuel it will run SLIGHTLY leaner as the temp drops and the air is more dense, shouldn't make enough of a difference to require any changes to the reg setting.
Thank you for taking the time to respond.That is correct, a choke is used with liquid fuel to get more liquid to air in the intake stream with the hope that enough will vaporize to get the engine to fire, then heat takes over and vaporizes the liquid and the choke is not needed.
With vapor fuel, esp NG which will not turn liquid (at sane temps and pressures anyway) a choke is counter-productive. You may need to press a primer button on the reg if the engine will not draw enough vacuum itself to open the regulator. This can be a problem on governed engines where they crank at wide open throttle, made worse by slow cranking speeds in the cold.
NG and Propane need a smaller spark plug gap than gasoline to ignite so be sure to check the gap spec's when running dry fuel for the setting for dry fuel.
NG will stay vapor well below -100 deg f IIRC and doesn't liquife until very high pressures. so none of LP's problems will effect running NG. Propane liquifes at -44 deg f at atmospheric pressure and the tank pressure drops with the temp. At -44 or below you could pour it in a gasoline tank (and if the rubber in the fuel pump didn't crack) burn it like gasoline! NG stays gas and since in most cases the gas is supplied by a pipeline not a tank, the pressure stays more or less constant on the supply.
In some areas, "propane" or more exact LP (liquified petroleum gas) is a mixture of propane and butane and butane liquifies at a much higher temp and this can cause lower tank pressure than pure propane. None of this matters if burning NG however.
Air alone can cool and frost at the throttle plate. so it is possible to get carb ice on a dry fueled engine. Ever noticed frost on a valve stem when deflating a tire?Carbs ice because as liquid gasoline turns to a vapor it cools , just like Freon.
Can condense humidity and ice up, just like cold coil in a refrigerator.
Vapor fuels are already a vapor so no carb icing.
Propane however does cool were ever it turns from liquid to vapor ( in tank, or heated vaporizer)
Nat gas is mostly methane.
Typically never a liquid, need very cold or very high pressure to do it, $$$$.
-- @ atmospheric pressure < -257 deg F
-- @ room temp, likely few thousand psi ... (even @ cold -121 deg F, need 625 psi)
I believe this is why many, if not most fuel injected cars still have heated butterfly valves for the throttle. There's no fuel anywhere near it.Timing will likely need to be advanced a bit if running NG only. Look to the engine Mfg for recommendations on plug gap and timing running dry fuel.
---------- Post added at 01:29:38 PM ---------- Previous post was at 01:27:09 PM ----------
Air alone can cool and frost at the throttle plate. so it is possible to get carb ice on a dry fueled engine. Ever noticed frost on a valve stem when deflating a tire?