Running engine dry

[Ice_2k]

Do you guys run dry at the end of the day or just empty the contents of the tank and let the fuel in the carb stay there? How'bout when preparing for winter?


Also, if I want to work on the engine (change the carb for instance), how can I best empty it so I won't get gas everywhere when opening it?

 

[RampageHopUps]

Do not run the engine out of gas. It puts the engine in a lean condition. If you won;t use it for a few weeks, then just dump the tank out.

For winter storage, I use Stabil gas conditioner in my lawnmower. You can run a few minutes worth of that in your carb and it won't gum it the needles.

 

[Ice_2k]

Ah, gas conditioner, ok. Didn't know that existed. Any advice on emptying the carb for working on it?

 

[designed2survive]

Ah, gas conditioner, ok. Didn't know that existed. Any advice on emptying the carb for working on it?

Pull out the intake fuel line (the one that go to the bottom of the carb) from the fuel tank. Then prime until the bulb is empty. Priming will pump the fuel back to the tank. Make sure you don't pull out the return line (the one on the top of the carb).

 

[Ice_2k]

Thank you!

 

[Ice_2k]

Sort of related to the topic: after turning off the engine, there is still gas in the carb, the fuel lines etc, right? So, when next starting it, what's the point of using the choke again? What will it achieve? If there was already fuel in the carb, doesn't this increase the risk of flooding it? I'm pretty sure I don't clearly understand why the choke helps the engine startup procedure, so maybe that's where the confusion is coming from.

 

[RampageHopUps]

You only have to use the choke when its cold out, or if you let the engine cool down after a few hours.

 

[Ice_2k]

yes, I know that, my question was more along the lines of "why does it work? HOW does it work?" I tried searching online but all I get to are real size car chokes, which don't choke it completely, the car starts with the choke on so I guess it's not the same thing. For that scenario I understand why a richer mix works. I just don't get it why in RC, it helps to richen the mix but then choke it so it won't start.

 

[RampageHopUps]

No idea on the theory.

 

[Dongskie]

when choked, less air comes in and more fuel comes in, so on cold starts it richens the mixture when there was initially more air than fuel, so when you crank it fires up then quits becuase the gas becomes more than the air in the crank case, then you open the choke valve so air would come in and equalize the mixture and it would continue running.

When you choke the engine while running it will richen-up until there is not enough ai in the mixture and it will quit.

I hope my understandin gwas correct

 

[Ice_2k]

yes, that's basically my understanding as well. The part I don't understand is why does that help? Why does making it fire and then die help it start after opening the choke and pulling the pull start again? Just because of the small heat that was created when it briefly fired?

 

[Dongskie]

Im assuming that when the engine had been in a rest for sometime, the air and fuel in the crankcase had evaporated thru the carb (hence 2T engines always smell gas) so it

During cold start choking it and cranking helps attain the correct fuel & air mixture in the crankcase during that process and fires up briefly then quits because the choke was still on because too much gas is in the crankcase.

Then we open the choke and so more air comes in and equalize the fuel/air mixture and continues to fire up.

 

[Ice_2k]

seems unlikely to me that there's enough room for the fuel to evaporate from the carb. But the rest seems plausible.

 

[Dongskie]

seems unlikely to me that there's enough room for the fuel to evaporate from the carb. But the rest seems plausible.

the carb on idle has a small opening, and when the engine is at rest, expanding gas vapor exits thru that specially with a hot engine.

 

[Ice_2k]

ah, ok. Didn't know that.

 

[designed2survive]

A choke is there to bring fuel quicker into the carb and therefore in the crankcase easing the starting procedure. Why does the engine needs choking? Because fuel evaporate. Proof is after a run, there is always some fuel in the prime bulb (in a good working carb). If you let the car sit for a day or two. You'll come back to find that there nothing left in the prime bulb. The engine needs a constant and regulated flow of fuel delivered to perform correctly. Choking helps you get to that needed flow quicker.

 

[Ice_2k]

makes sense, thanks

 

[phreerider]

choke "stops air" and the piston movement pulls gas into crank case .... now the gas vapor pushed to the top of the cylinder...the vapor/air mixture ignite for combustion reaction which drives cycle again. the negative pressure side(carb) of the mill sucks air and fuel to combust in chamber for stroke power and moves to positive pressure side (exhaust)

with the volatile nature of gas, it will be gone after shut down in a short amount of time. this is temperature dependent, the ambient temp as well as motor temp. a hot motor with a wet case will pop with one pull but can be easily flood with TOO many snap pulls. a cold motor ---> choke OR 4-5 full slow pulls

a "choke kill" literally drowns the ignition...to wet to burn, only vapor will burn.

after a 30 min run i shut down, about 10 min cool period , then 4-5 full slow pulls and pops in about 2 snap pulls.. but if its cold below 50F finger choke, one snap pull

practice! this practice contains feel, sound and smell ...that will tell what to do

no theory at this point, its just experiential -->practice

 

[Ice_2k]

Great explanation, thanks

 

[Ice_2k]

For winter storage, I use Stabil gas conditioner in my lawnmower. You can run a few minutes worth of that in your carb and it won't gum it the needles.

I bought a bottle of STA-BIL, just one question: the instructions say to leave the fuel tank 95% full to avoid condensation. Do you do that? Seems to contradict all the advice given here.