Carburetor ice

[CROSSBOLT]

Had something happen today that I have not experienced in years - carburetor ice! Old Trusty Echo weed eater, 'scuse me! String trimmer faltered. One of those, "what now?" monents. Backed off the throttle just a bit and let it idle for just a few seconds, 10 to 15, then powered up normally. That little bit was all it took to melt the ice. Hot today, 88 to 93 so far with 75% + humidity puts anything with a carb in the zone for ice. This is practically non-existent in fuel injected engines. Why? I will bet a bunch of you know this! The venturi in the carb where the fuel is sucked into the low pressure area drops the temperature drastically freezing any moisture in the air. Cars for years had "heat risers" to combat this: a mechanical connection between the intake and exhaust manifolds to heat the intake air. Aircraft with piston engines had a lever ot pull knob to vent heated air into the carb intake. You knew when the knob was pulled because the power dropped! But it got rid of the ice! That ice can form rapidly enough to stall the engine.

[Iahawk]

wow, I wasn't aware of all that...thanks for the interesting info!

[hypophthalmus]

I'm surprised that it's an issue when it's so warm out.

My bike has two electric carburetor heaters to combat this, but they don't turn on until it's under 50ish F (I think).

[CROSSBOLT]

Warm has little to do with the formation or that's what they said in flight school. It seems more likely on low throttle so that's why pilots are instructed to pull on carb heat prior to landing. It is pretty insidious.

[kymcogrampa]

You're right Karl, My Echo weed muncher, err...grass trimmer, is the best one I've ever used. That being said, it is a 2 stroke and these engines burp and fart more than a 4 stroke. Is there a chance that it could also be something else? eg; water in gas from the high humidity, spec of dirt going through the jet, etc...

Inquiring minds need to know!

(I hope you don't mind a friendly exchange from your northern neighbour? If you do, I'll quietly bow out like any mild and meek Canadian!)

My '03 Yamaha Royal Star Venture had 4 carb heaters to help atomize the gas on start up until the engine got up to temps. It allowed a leaner carb jetting to help it pass the emission standards of the day. On a cold winter day, I'd leave the ignition on for a minute or so before the carbs got warm enough to atomize the gas. Neat setup. The 2018 Yamaha Vk540 snowmobile just got a carb heater in order to pass the stringent emission standards. One benefit is that it got a great mpg improvement. One drawback...guys are having to drill out or up size their pilot and main jets, as they are running too lean and burning down their engines!   

Rene

[CROSSBOLT]

You keep on exchanging! Do not consider Canadians anything but American, except your government! Most of American government consider American citizens the enemy!

Nope on water in the gas. Considered the tiny flapper valves failing but idling or shutting down cured the stumbling so occluded carb ice the culprit.