I have a couple of motorcycles with fuel shutoffs, a lawnmower with one, and can disconnect my outboard fuel line to run carb bowls dry. I prefer to shut off these engines without fuel left in the carb bowls for several reasons, to not let any fuel leak into the engine, and to prevent gum or deposit formation until the next run. I envision the engine heat warming the cool fuel in bowls during shutoff expanding the fuel and causing some to leak into the intake tract.

I'm wondering if it would be better to run just a short while with the fuel shut off to lower the fuel level in the bowls rather than run it all the way out. Two things might happen with mostly empty fuel bowls, since running the engine until it stops still leaves some fuel in the bowl. One is clean metal in the bowl and carb is now exposed for corrosion. This is like why it is recommended to leave fuel tanks full on storage, exposed tanks can corrode. (plus leave air space for condensation, less of an issue in a small carb bowl)

The second problem that small amounts of fuel in a bowl causes it to evaporate and leave deposits where a full bowl would remain liquid for some time. I think you want fuel in the bowl unless the machine is layed up for long periods, then it might be good to introduce some kind of corrosion inhibitor into the bowl.

I would treat the fuel and leave the system as is. Maybe start the machine once or twice over the winter. Should be good to go come next summer.

I treat my motorcycles fuel and here in the Yoop it sits for 6 months. It helps that I can get ethanol free premium here.

Any motor I have, I know that may not be run for. While, I run the carb dry after shutting fuel cock off

Start engine.

Let idle.

Turn off petcock.

Let engine die.

Do not use fuel with ethanol.

It's hard to find ethanol free fuel where I live but I make sure that is in my atv when I am not using it. I add Stabil and just start it up once a week and let it run until warm then shut it off. The dual carbs on it are a pain to remove and install and I have had them out several times working on jetting so I prefer not to have to pull them after letting fuel sit in them for months. I will never buy an ATV/motorcycle with carbs again.

I was told that with two cycle, oil added, it is best to shut the fuel off and when the engine just starts to sputter... shut it off quick...

If the engine is only going to sit for a month or three I think an additive and ethanol free gas is probably a better choice.

Our antique tractors, built in the '30's, with magnetos and hand-crank start, usually only get started every 3 months or so, and do set longer during the winter months. Dad always shut off the fuel at the sediment bowl and let the engine run until the carb was drained, regardless of occasion. I try to use higher octane, ethanol-free fuel from our local Sunoco station in those, and also mix in some aviation fuel to extend the life of the fuel in the tanks.

For my seasonal engines, such as snow blower or lawn mowers, I use ethanol-free fuel and tend to use Stabil at the end of the season, leaving the fuel in the systems. I do try to start them once or twice in the off-season, but sometimes that doesn't happen. So far, no issues.

My father-in-law, who worked for the local John Deere dealer his entire career, had often said that the newer engines on mowers and other power equipment are sensitive to ethanol-based fuels, so I make all reasonable attempts to use ethanol-free, in at least the mid-to-higher level octane ratings.

I do use the high-test Sunoco fuel when mixing for two-stroke engines, as the usage of those engines for me are more sporadic and the fuel tends to set around longer.

pure-gas.org will help you find it.

quote:

Originally posted by mrvmax:
It's hard to find ethanol free fuel where I live but I make sure that is in my atv when I am not using it. I add Stabil and just start it up once a week and let it run until warm then shut it off. The dual carbs on it are a pain to remove and install and I have had them out several times working on jetting so I prefer not to have to pull them after letting fuel sit in them for months. I will never buy an ATV/motorcycle with carbs again.

You can buy True fuel in cans for 4 cycle engines.
92 octane rated, a bit pricey but for what you are doing, it would be a few dollars well spent.

Drain fuel tank, add TrueFuel run around the block, shut it down, turn off fuel supply and just add a squirt of light oil, leave plugs out, and crank it before starting it up.

If you are on an area where moisture is an issue, add an oz of oil to the fuel before running.

Do the float bowls on your motorcycles not have drain screws? The Keihins and Mikunis on my motorcycles all had drain screws on the float bowls, so there was no need to leave any fuel in the carbs. I never worried about corrosion inside a carb. The materials the carbs are made from are fairly corrosion resistant.

Go to a small airport and get some 100LL a gas. It’s usually about the same price as no ethanol and has good fuel stability. Put it a touch of quality 2 stroke oil if you like.

I was always a believer in preparing for a lengthy period of storage ( winter for the landscape tools and summer for snow removal equipment) by draining the fuel tanks and running the equipment until fuel bowls were empty. After experiencing two problems related to dry gaskets or membranes, I've changed my preparations.

I had a three year old heavy duty weed cutter that I couldn't start and took for repairs. After completing the repair, the service tech asked if I drained the fuel for storage. He said that the flexible membrane used in many small engines as a "fuel pump" split from being dry. He recommended keeping the fuel system wet with fuel mixed with fuel stabilizer.

I also have a muscle car from the 60's with a stock Holley double pumper carburetor. The car is only used in the summer months and stored all winter. One spring day, I noticed that the top of the intake manifold was wet with fuel but I couldn't find the source of the fuel. The following spring, I had a similar experience except that there were pools of gasoline lying on top of the intake manifold and gas was still leaking from both fuel bowls. Yikes! When I disassembled the Holley, it was apparent that the gaskets on the bowels had dried out, shrunk and pulled to the inside of bowls in the area of their longest length between the attachment bolts. I had this experience the following spring as well and I know I was careful to torque the fuel bowls properly when I previously reassembled the carburetor.

Since those experiences I avoid draining the systems dry for periods of long storage. I have not had problems with stabilized fuel, but I am considering the advice of others to use 100LL gasoline for these applications. Avoiding ethanol and using the low lead fuel has other benefits which may justify the added expense. Tree huggers -- I await your replies.

So... This is not about fasting to lose weight?

quote:

Originally posted by Av8nShooter:
Since those experiences I avoid draining the systems dry for periods of long storage. I have not had problems with stabilized fuel, but I am considering the advice of others to use 100LL gasoline for these applications. Avoiding ethanol and using the low lead fuel has other benefits which may justify the added expense. Tree huggers -- I await your replies.

Yup, had the same experience with quads. Switched them over to 100LL after that, just like I’d done long before on the chainsaws.
Bear in mind that 100LL, while lower than the 100/110 you use to get in Mexico (may still do, I just haven’t flown down there in a while), does have lead in it.

If you’re a tree hugger that may bother you.

There is at least one, and I think two, FAA approved unleaded avgas replacements for 100LL. They’re probably more expensive, but at some point they’ll likely replace 100LL. What makes 100LL so great is that it is long term stable and doesn’t have all the crap that turns to varnish in the garbage they sell at the gas station. I’d expect that the FAA required testing to show the same properties in the “green” replacements.

I own a car with multiple Weber Carbs. I always shut the fuel pumps off and keep the engine running until the carbs run dry. This has saved me many $$ in parts and time by not having to rebuild gummed up carbs. I have been doing it for over 20 years now.

quote:

Originally posted by old rugged cross:
I would treat the fuel and leave the system as is. Maybe start the machine once or twice over the winter. Should be good to go come next summer.

This, also you don't want to run 2 cycle engines dry. The fuel/oil mixture travels through the bearings first to lubricate them before getting to the combustion chamber. Running them out of fuel means the bearings run dry prior to the engine shutting off, creating additional wear.

From someone who has a zillion seasonal carb gas engines. The winning strategy for everything from 1 cylinder to 12 powered by gasoline with a carb is to get high quality ethanol free fuel into the fuel system. Do not run till dry the the gaskets and seals in the carb don't like it, and if you have ever run ethanol fuel in the same engine its a death sentence.
Ethanol free fuel is available everywhere. My preferred source is race gas, but I have it always around. Your choices are probably race gas (there will be somewhere locally that sells it), the cans at stores that sell small engines, and avgas. I can promise you that a motorcycle with race gas will start happily in the spring. I would turn off the petcocks so a float issue doesn't run the fuel from the tank into the carb and then flood the engine.
If you insist (stupidly I would say) to running things dry on any carb will be a drain and you can remove it to get the last little bit of fuel out of the system. There is literally no reason to run the engine to starvation, just drain the carbs with a shutoff upstream.

Many good suggestions, many are most applicable to off season storage. I was mainly talking about normal intermittent use of toys, not seasonal storage.

Several responses indicate some problems with gaskets drying out in empty carb bowls. Most final generation carbs on motorcycles and outboards don’t have gaskets in constant contact with fuel, just O rings.

I think unless I foresee any machine with a petcock sitting for a month, I’ll leave the carb bowl mostly full. When I empty the bowl for long lay-off, I’ll try to introduce some type of corrosion inhibitor into all parts of the fuel system, even the drained bowl. Fuel stabilizer and 1 oz per 5 gallons of gasoline of TCW3 two cycle oil hopefully will prevent corrosion in an empty bowl.

quote:

Originally posted by hrcjon:
Ethanol free fuel is available everywhere.

Incorrect, it is not available everywhere, you just think it is.