should a fuel shutoff valve be used?

[The motor guy]

How come some manufacturers use fuel shutoff valves? I've never really seen the point of one other than to be able to turn the fuel off and only lose whatever is in the fuel line when you take the carb off. Isn't it best to leave the valve in the on position to prevent the bowl from going dry and causing the rubber parts to dry out?

 

[Quest]

fuel-related elastomeric parts such as viton, etc. does not experience "dry out" regardless of fuel present or not.

main purpose of fuel shutoff valve is to reduce fuel from filling the bowl and evaporated through various orifice, jets, etc. where it will get out and make the storage area stinky, and also reduction in gumming of the carb bowl.

Q.

http://www.fbs-online.com/Centre/Prod/Viton-chem-com-res.htm

 

[The motor guy]

Originally Posted By: Quest
fuel-related elastomeric parts such as viton, etc. does not experience "dry out" regardless of fuel present or not.

main purpose of fuel shutoff valve is to reduce fuel from filling the bowl and evaporated through various orifice, jets, etc. where it will get out and make the storage area stinky, and also reduction in gumming of the carb bowl.

Q.

http://www.fbs-online.com/Centre/Prod/Viton-chem-com-res.htm


So are all rubber parts in a carburetor made of Viton then?

 

[The motor guy]

I know that everytime I've stored a carbureted engine by running it out of gas I've always had problems after that with the small amount of fuel left gumming up the carb.

 

[Warstud]

There's a few reasons for a shutoff valve:

1) In case you may a have leak some where... there's not gas dripping out everywhere.

2) When storing...you can run the fuel out of the system.

3) If you have to remove carb.

If you do decide to install one...make sure the arrow on the valve points toward the carb.

 

[Quest]

unless the OPE engine and carb are 30+yrs old, otherwise: if they are made within the past 15 yrs, chances are, the elastomeric seals used in carb where they come into regular contact with fuel are all made of viton.

I've seen some very old carbs that the parts are made of buna-N, but that was for carbs built in or before the 60s...

Also: when in doubt: never soak any carb in carb cleaner: chances are: the mating surface kind of gasket/seals for certain hidden air passages are made of non fuel/mineral oil/solvent resistant materials, and they will disintegrate if soaked in carb cleaner (or prolonged exposure to solvents, such as carb spray, etc.)

Ask me why I knew about this part...

Q.

 

[andyd]

On my sitdown mower, I run the carb dry after every use. The engine is a B+S 11 hoss I/C flathead. Since I started doing this, I havent had to clean the carb once. I also use a little MMO in the gas. My guess is that the amount of gas left in the carb isnt enough to varnish it. My old Lawnboy will drain the tank if I dont use the shut off. The shut off doesnt work on the Toro mower.

 

[Corvette Owner]

I experienced fuel in my oil with my Snapper Riding Mower, their fix was to install a fuel cutoff valve. New Snappers have one also. BTW, this mower is 8 years old and never before had any problems.

I always cutoff the fuel a little early, so engine runs a bit to lower gas in carb.

 

[skully]

main purpose of a shutoff is in case of float/needle failure the engine doesnt get filled with fuel resulting in engine damage due to fuel dilution upon starting/running. every carbed engine should have one, cost cutting and space usually result in an engine not having one.

 

[lars11]

"sitdown mower" is a great name for the rider. I will start using it when commenting my (young and fit) neighbors with a rider and a small yard. It's even more hilarious in Swedish, associating to all sorts of stuff for really old people.
Originally Posted By: andyd
On my sitdown mower, I run the carb dry after every use. The engine is a B+S 11 hoss I/C flathead. Since I started doing this, I havent had to clean the carb once. I also use a little MMO in the gas. My guess is that the amount of gas left in the carb isnt enough to varnish it. My old Lawnboy will drain the tank if I dont use the shut off. The shut off doesnt work on the Toro mower.

 

[andyd]

The " sitdown " started out as a '77 Cadet 80. It is running but, has lost its hood and a fender. Its sitdown is a wicker bar stool.

 

[Jasonenginetech]

Originally Posted By: motor_oil_madman
I know that everytime I've stored a carbureted engine by running it out of gas I've always had problems after that with the small amount of fuel left gumming up the carb.


^^This^^ Hear it from customers almost everyday, "but I ran it out of fuel."

 

[lumpy_grits]

OP-With your Honda genny. The fuel shut off and engine shut off are the same switch.
Honda has sold how many gennys?
LG

 

[DuckRyder]

Is this a "Honda Generator" and if so what model or is it a "Generator with a Honda Engine"?

 

[mitsuman47]

Originally Posted By: andyd
The " sitdown " started out as a '77 Cadet 80. It is running but, has lost its hood and a fender. Its sitdown is a wicker bar stool.

With a description like that, we deserve a pic of this beast.

 

[Jasonenginetech]

Originally Posted By: lumpy_grits
OP-With your Honda genny. The fuel shut off and engine shut off are the same switch.
Honda has sold how many gennys?
LG


And I make a lot of money cleaning carbs on EU2000's. The customer's that have tried the VP small engine fuel have had no starting issues even after a year of storage.

 

[dave123]

Originally Posted By: Jasonenginetech


And I make a lot of money cleaning carbs on EU2000's. The customer's that have tried the VP small engine fuel have had no starting issues even after a year of storage.


VP SEF is great fuel to use and better for shutdown and storage I now buy it by the 5gallon pail for most of my OPE