Gas Shutoff's

[Robin Veerman]

A couple of things for you guys. Turning off the fuel and letting the engine starve to empty the carburetor is actually not quite what happens. Yes the engine will starve and stall, BUT there is still a tablespoon or two left in the bowl. Almost all Honda small engines have a convenient drain screw. My Honda generators actually have drain lines too. Drain your carburetor for best results or you are only delaying the issue.
Secondly, ALL gasoline in Ontario (all of Canada?) now has ethanol. Which was eventually fazed in and now the norm since spring of this year. Small engines like regular grade gasoline, unless specified, so run regular to reduce carbon buildup. I also run a quality fuel treatment…
MY 2 cents

 

[sunandsand]

Once a fuel tank is gummed up from ethanol, how can you clean it out?

Local radiator shop said they can steam clean it, but it will ruin the paint. On two classic BMW motorcycles (1952 and 1968) that is not an option. Also have a JD Gator (rescued from someone's back yard) which I think has a plastic gas tank - had ethanol goo in it, so I'll replace the carb, fuel pump and gas lines (parts from eBay) but I still have to clean the tank.

On another motorcycle, I avoid ethanol-laced gas entirely. Fiberglass tank, utterly unobtanium, ethanol will eat it. Pair of 40DCOE Webers, these things make Rubik's Cube look like a nursery school toy. Solution for this one is to avoid ethanol gas period, 100%.

All the bikes want leaded gas or they'll have a valve seat recession problem pretty quickly. The BMWs have a retrofit kit available ($$$), the other one gets "you gotta be kidding" or "WTF is that thing anyway?" so I'll use an additive.

Lawn mower and generator get run with the fuel valve off (or the tank almost empty) until they stop. The mower is probably 40 years old (!), has a 3.5 hp Tecumseh, replaced the carb once about ten years ago, runs fine.

Best Regards,
Mike/Florida

 

[Jaygyver]

I guess that's the only thing I've been lucky on then. I had no problems storing 5 gal cans of gas for a year or so, then I got nervous reading all the horror stories and started using the normal storage Stabil in them year round and haven't had an issue yet. Knock on wood. I do try to keep the gas tanks on the machines topped off when done using them. Just pump gas at Fred Meyers.

I have the cans in my unheated/insulated shop. For the last few years I've gone to 4-14 gal tanks, 2 gas and 2 diesel, got rid of those dang 5 gal cans. I make sure the cans are sealed for sure. I might refill the bulk tanks 3 or 4 times a year to maybe once a year, just depends on how much motivation I have that year I guess.

 

[eKretz]

Whether this happens or not is very dependent on the conditions. One, how well sealed the fuel system is. Note that it almost never happens on fuel injected vehicles. That's because the fuel system is completely sealed and there is also normally a vacuum pulled on the system while the engine is running. That limits the amount of humidity that gets into the system and helps eliminate it if it does get in.

Another factor is frequency of use. If you use the equipment every day or even every week, it's less likely to keep any humidity that is absorbed into the fuel (ethanol is hygroscopic) sitting in the float bowl. That water sitting in the float bowl separates out from the fuel over a relatively short amount of time once you set the equipment down for the day, and that's what corrodes the aluminum and brass in the carb and causes all the trouble. If you let it sit there for extended durations (especially if this is repeated) it's going to clog the carburetor eventually. If you keep clearing it out regularly by running the equipment, that's far less likely to happen.

If it's frequently very humid where you live, if you keep your equipment in a space that's not temperature and humidity controlled, and if you don't use the equipment frequently or you let it sit over winter, you are almost guaranteed to have these problems within a year or two of buying a brand new piece of carbureted equipment if you run fuel with ethanol in it. Using non-ethanol fuel will very nearly completely eliminate these kinds of problems.

Sta-Bil will not prevent this either. Keeping the fuel tank as near to completely full as possible helps a little because it will prevent humidity in the airspace above the fuel in the tank from absorbing into the fuel. Shutting off the fuel supply and running the engine dry after every use will help, but won't always completely solve the problem - that's dependent on how "dry" the bowl actually gets. If your carburetor's float bowl has a bottom drain and your equipment is stored in sub-optimal conditions as I described above, use it!

A diesel engine will generally not have any of these sorts of problems because they do not use a fuel that is hygroscopic. If water gets into their fuel it can cause similar issues, which is why diesel engines almost universally have a water separator.

2-strokes are indeed not good to run lean, but this is generally more important at full throttle, high load and high RPM. I used to run my 2-stroke dirtbikes dry at the end of the day *all the time* with nary an issue. They don't go lean until the last so many seconds of operation and basically you're just idling the engine with no load. If you're that worried about it, check if there's a float bowl drain. I have done it on two strokes many many times from dirtbikes to chainsaws to weed trimmers and never had any issue. I've got a 2 stroke John Deere (Homelite relabel) trimmer that's almost 25 years old and still running strong on the completely original engine with zero carb issues that I run dry at the end of every mowing season.

 

[eKretz]

Oh, and for cleaning out the problem, the only way is to pull the carb and disassemble it down as far as you possibly can into separate pieces. Then clean out every small passage that you can with a wire or similar. I then will soda blast the entire inside of the carburetor. Then blast out with brake cleaner or carb cleaner and blow out thoroughly with compressed air. Reassemble and run it.

 

[mjonesnh]

I guess that's the only thing I've been lucky on then. I had no problems storing 5 gal cans of gas for a year or so, then I got nervous reading all the horror stories and started using the normal storage Stabil in them year round and haven't had an issue yet. Knock on wood. I do try to keep the gas tanks on the machines topped off when done using them. Just pump gas at Fred Meyers.

I have the cans in my unheated/insulated shop. For the last few years I've gone to 4-14 gal tanks, 2 gas and 2 diesel, got rid of those dang 5 gal cans. I make sure the cans are sealed for sure. I might refill the bulk tanks 3 or 4 times a year to maybe once a year, just depends on how much motivation I have that year I guess.

Red Stabil seems to max out for me at about 1 year storage. Switched over to the Marine Stabil and a splash of Seafoam and will get me through 2 years stored in can or in carb.

 

[SPYDERLK]

I with the I don’t have any fuel problems group but I’m of the fill it to the brim before storage mindset.
I get that everyone’s experience is different and I believe local climate is a factor but heck this stuff is what forums are for right?
My opinion for this is personal experience and I’ll elaborate…

Running it dry = can’t be done. Shut valve and engine will die before bowl is truly dry leaving product to evaporate and leave “lacquer” that eventually flakes off and gets under needle and looks like grit. It can also get past the needle and plug passages. Empty bowl is an environment for repeated condensation development.

Filling and vale open = no air space for condensation in bowl or tank.
With a properly working system as the fuel evaporates from the carburetor via the vent the float will allow it to refill eliminating lacquer and moisture.

Especially would not run a 2-stoke out of fuel because the leaning out of the fuel air as it dies is about the worst thing you do to a 2-stoke GAS engine that is when you burn holes in pistons. Note that it’s not good for 2-stroke Diesel engines either because shutting off the fuel would remove needed lubrication from the injector pump and brings a whole bunch of other requirements to get it running again.

Can only recall one instance of difficulty in getting a motorcycle started in the spring of the pre-ethanol days in the early 90’s and that was the first time and the last time my buddy talked me into using Seafoam.

I buy and store my gasoline and diesel fuel in 55 gallon drums that were new and impeccably clean because they were food grade drums.
Drums are kept sealed when not needed and it takes me about a whole summer or longer to use a drum of gas and almost three years to use up the diesel in my little 25hp tractor that’s main purpose is snow removal.

I use No fuel additives or conditioners other than what comes in the fuel when I buy it.

But whatever works for you and lets you sleep at night is the right thing to do.

And I hope that for the original poster that they discover it’s as simple as a bad batch of fuel.

It really doesnt take more than a few months in the summer to come real close to screwing up the carb if you leave the gas on. I came back to my mower after such and it wouldnt start. Drained the bowl and dumped it on concrete. It smelled like lacquer; couldnt light it with a propane torch. Ran in fresh gas from the tank and it started right up. I cut it off without using it and it wouldnt start the next day.

What happens in a carb is the volatiles evaporate to be continuously refreshed with new gas from which the volatiles also evaporate. The less active residue concentrates. Some actually precipitates in the bowl. Fresh gas may start it, but it also dissolves the precipitate slowly. This spoiled the new gas on the bottom near the main jet preventing start the next day.

I repeated the drain refresh, started it and mowed the lawn. No more trouble. Dodged the bullet.

 

[ultrarunner]

1970's international cub cadet garden tractors came with glass sediment bowls that had shutoffs in them. Early 1980 troy bilt tiller had shut off. honda gx engine had shutoff. The old Briggs that had fuel tanks mounted directly to the carbs didn't have shutoffs.

Leaving any gas in the carb over the winter always meant having a stuck carb needle in the spring in my experience.

I only use non-ethanol gas in small engines.

Many of my old cars have fuel shutoff valves.

 

[ultrarunner]

It really doesnt take more than a few months in the summer to come real close to screwing up the carb if you leave the gas on. I came back to my mower after such and it wouldnt start. Drained the bowl and dumped it on concrete. It smelled like lacquer; couldnt light it with a propane torch. Ran in fresh gas from the tank and it started right up. I cut it off without using it and it wouldnt start the next day.

What happens in a carb is the volatiles evaporate to be continuously refreshed with new gas from which the volatiles also evaporate. The less active residue concentrates. Some actually precipitates in the bowl. Fresh gas may start it, but it also dissolves the precipitate slowly. This spoiled the new gas on the bottom near the main jet preventing start the next day.

I repeated the drain refresh, started it and mowed the lawn. No more trouble. Dodged the bullet.

I have an old Clinton engine and the fuel bowl has a spring loaded plunger making it easy to drain… Seen drains on the wings of small planes too.

I dread how many bad carbs I will find around here with all the equipment stored.

I do believe a cool even temperature year round is a plus…

Lots of the mower problems I help friends with are stored basically outdoors in a shed with large temperature swings.

I did a little experiment with a clean dry 5 gallon container with a small vent hole on the shed.

A cup of water accumulated in the course amid a few years…

 

[MossRoad]

I have an old Clinton engine and the fuel bowl has a spring loaded plunger making it easy to drain… Seen drains on the wings of small planes too.

I dread how many bad carbs I will find around here with all the equipment stored.

I do believe a cool even temperature year round is a plus…

Lots of the mower problems I help friends with are stored basically outdoors in a shed with large temperature swings.

I did a little experiment with a clean dry 5 gallon container with a small vent hole on the shed.

A cup of water accumulated in the course amid a few years…

I've never seen a small aircraft without a fuel sump under the tanks. It's at the low point. You push a glass tube up under it and drain a few ounces into it, then look for water in the fuel. It's surprisingly common to see a few drops in there. It could lead to freeze up at altitude.

When I worked at the airport, we had to drain a couple gallons from each 100 octane fuel truck every morning and check for water. Then we'd dump it into a ground waste tank for later pickup. It cost the boss $$ to have that tank sucked out every year, so we convinced him to let us put it into our coworkers 67 Corvette with the 327/350 option. He'd take a parking cone and turn it upside down and use it for a funnel to pour the fuel from the bucket to the tank on the car. You could tell when he was burning that fuel in the car. The exhaust smelled different.