Should you turn off gas between using Mower?

[jrcowboys]

Guys:

I typically switch off the cuttoff valve on both my mowers between uses (typically 1-2 weeks). Note: the riding mower (B&S engine) has an electrical cuttoff switch on the carb. I added a another cuttoff valve on the riding mower to hopefully prevent gas fumes in the garage (it seemed to help).

My question is: Is this the best practice to prevent crud buildup in the carb? Seems like the gasoline would evaporate in the carb,leaving it dry,but is this a good thing?

Would appreciate your thoughts.

JR

PS: had to adjust the valves on the B&S engine or it would hardly start, is this typical of B&S engines?

 

[expat]

Originally Posted By: jrcowboys
Guys:

I typically switch off the cuttoff valve on both my mowers between uses (typically 1-2 weeks). Note: the riding mower (B&S engine) has an electrical cuttoff switch on the carb. I added a another cuttoff valve on the riding mower to hopefully prevent gas fumes in the garage (it seemed to help).


I did the same last year, since, I have noticed how much Gas I must have been loosing due to evaporation or slow leaks.

Yes, shut the gas off.

 

[The motor guy]

what you're doing will leave crud in the carb bowl. What happens is the fuel evaporates and then leaves a white powdery residue behind. Just leave the fuel valve open. I don't know why they put those on. I have one that came with my mower that's been there for 8 years and I've never turned it.

 

[suspiciousmind]

Well, the carb can decide to leak while they rest and create quite a fire hazard.....turn the valve off.

 

[SwampSurvivor]

Isn't a carburetor just a glorified fuel leak anyway?


... can't remember where I heard that joke.

 

[Hokiefyd]

Originally Posted By: motor_oil_madman
I don't know why they put those on.


The reason is because the needle in the carburetor can stick open, for a variety of reasons. It's usually due to grit in the needle or seat, or the needle could become jammed somehow. Anyway, if the needle sticks open, all of the fuel in the tank will drain out through the carburetor. It may drain into the engine/crankcase, or it may drain out through the air filter to the floor. Either way, it's not a good situation.

I hear you on the evaporation issue. Honestly, I don't use the fuel switches either.

But that's the reason.

 

[Sam_Julier]

I turn the fuel valve to off to shut off my Honda 160cc mower. Honda recommends this to combat the effect of ethanol. This has allowed me to extend carb replacement to 3 years.

 

[expat]

Originally Posted By: Sam_Julier
I turn the fuel valve to off to shut off my Honda 160cc mower. Honda recommends this to combat the effect of ethanol. This has allowed me to extend carb replacement to 3 years.


You replace the carb every 3 years!

I have never replaced a carb.
Perhaps clean it, but that might be after 10 years, or a multi year lay-up.

 

[RobertISaar]

if evaporation left behind significant deposits, perhaps cut fuel flow and let the engine drain the bowl before putting it away?

 

[bepperb]

We've had ethanol mandated here at 10% since 1996. I have a 1993 mower on the original carb. If you're replacing yours every 3 years something is very wrong.

 

[old1]

Ok, here is a subject of which I can comment on with some expertise. I have been a professional lawn mower/ small engine mechanic for well over 40 years now. Most of the modern mowers don't have gas shut off valves and those that do---Well to shut off or not is largely a personal call. YES, I have seen times where the needle valve sticks, but it is rare. Also I firmly believe that letting the gas evaporate out of the carb bowl will cause gumming. Even if you run the engine till it stops. That may even be worse, as it will stop running before it is DRY, and leave a small amount of fuel to evaporate. None of these evap. problems will cause a problem immediately, possibly not for a couple seasons of use, but it will eventually cause a problem. So you kinda balance the chance of a leak against a dirty carb, take your pick. I use a 40+ year old mower and have only cleaned the carb once since new. Season to season storage is an even bigger problem than week to week. I have found for my self that adding a double dose of any of the gasoline stabilizers, then filling the tank FULL and then running the engine a few minutes to get the stabilizer into the carb. seems to do the trick for me and my customers. Just my 2 cents.

 

[tnt31]

Originally Posted By: jrcowboys
Guys:
PS: had to adjust the valves on the B&S engine or it would hardly start, is this typical of B&S engines?


I believe it is. Happened with my 19.5 B & S about two months ago. I found a lot of youtube videos about it. However it was still under warranty and a sears tech came out and fixed it in less than 10 minutes. Based on what I saw him do one of the valves was a good bit off.

 

[thr_wedge]

I run my lawnmowers until I hit a rock/steel pipe, destroy the blade, and ruin the engine.

 

[TFB1]

Originally Posted By: old1
Ok, here is a subject of which I can comment on with some expertise. I have been a professional lawn mower/ small engine mechanic for well over 40 years now. Most of the modern mowers don't have gas shut off valves and those that do---Well to shut off or not is largely a personal call. YES, I have seen times where the needle valve sticks, but it is rare. Also I firmly believe that letting the gas evaporate out of the carb bowl will cause gumming. Even if you run the engine till it stops. That may even be worse, as it will stop running before it is DRY, and leave a small amount of fuel to evaporate. None of these evap. problems will cause a problem immediately, possibly not for a couple seasons of use, but it will eventually cause a problem. So you kinda balance the chance of a leak against a dirty carb, take your pick. I use a 40+ year old mower and have only cleaned the carb once since new. Season to season storage is an even bigger problem than week to week. I have found for my self that adding a double dose of any of the gasoline stabilizers, then filling the tank FULL and then running the engine a few minutes to get the stabilizer into the carb. seems to do the trick for me and my customers. Just my 2 cents.


Here's someone living in the real world and understands what's going inside that "ahem" dry carb, I fully agree with that statement... Keep some Sta-Bil in the fuel and there won't be a issue... I never use the shut off or run it out of fuel unless the tank just happens to go dry while I'm cutting...

Yes I store it wet at the end of season with whatever fuel was in it at last cutting... Yes my fuel is always treated with Sta-Bil and no I haven't had any issues...

 

[Dean85]

Agree with old1's post. I have been working on small engines for about 20yrs. I never use the fuel shut off or store the carbs dry. A carb stored with Ethanol fuel can develop issues with the fuel deteriorating over the storage period, causing gum and varnish to form in the carb. I think it also depends on where one buy's their fuel. IMO storing a carb with Ethanol fuel treated with Stabil/MMO or non Ethanol fuel, is better than storing them dry, unless you drop the float bowl, completely dry the carb and spray with WD-40. Residual fuel that may stay in the fuel line or carb due to running the unit out of fuel, can easily cause problems when an engine is taken out of storage. I am lucky to have access to Non-oxygenated fuel and use MMO in all my OPE's. The Non-Oxy feul is about $.40 per gallon higher, but I think it is worth it. I tell people when it comes time to store their OPE's, store it full of fresh fuel with either Stabil, MMO or Non-Oxygenated fuel for trouble free performance. Of course by doing that, I do not see as much repairs except for oil changes and blade srarpenings.

ps. It is not uncommon to have to adj the valves on a B&S engine. Did it help?

 

[Hokiefyd]

I, too, store all my OPE "wet" and have never had an issue. I own two Honda small engines (a GCV160 and a GXV140) and neither one has ever had any carburetor service. Both run 87 octane E10 only, treated with fuel stabilizer.

 

[exranger06]

Well, I store all my equipment dry and have never had an issue either, so.....??? Before I put my equipment away for the winter, I pour some Stabil in and run it long enough for it to get to the carb. Then I drain the tank, start it up again and let it burn up whatever is left. The Stabil is just for any residual fuel left. I recently took the carb bowl off my 21 year old tractor and it was spotless inside, and that was the first time it was ever removed. I never had a carb problem on my 15 year old push mower either. And I use nothing but E10 with no additives during the mowing season.

 

[jeepman3071]

The only issue I've seen with storing equipment "dry" is that the rubber gaskets inside the carb tend to dry out. This problem is amplified in the case of chainsaws and other equipment with diaphragm style carburetors.

I only use MARINE stabilizer, and fill the tank and add the stabilizer before storing the equipment. I run the equipment for a bit to make sure the stabilizer works its way into the carb, and then shut it down. I haven't experienced any problems since doing it this way, and neither have other people around me who do it as well. Its easier than running engines dry, and there is less risk of the gaskets drying out and cracking.

I rarely see gaskets dry out, but when it does happen its usually on a chainsaw, weed trimmer, or other small engine that requires a lot of work to take apart.

 

[itguy08]

I'd say no.

I add Sta-Bil and Marvel's Mystery Oil to my OPE Gas (except in the case of 2 stroke where it's just StaBil). Typically store wet for everything except the snowblower. I write the date I get the gas on a label and rotate it out every 6 months or so (I store 12 gallons) - into the car it goes after 6 months. No problems due to gumming up since 2008 and I use regular old pump gas.

Recently I had a surging problem with my 2008 push lawnmower with the B&S flathead (happened right after we got a new riding mower - jealousy?) Since I figured carb issue, I dropped the bowl. Clean as a whistle but with some sediment at the bottom. Looked to be regular old dirt, which would make sense as this engine has no fuel filter. Cleaned that, a shot of carb cleaner in the jets at the nut, and in the top holes (to reverse flush it), popped it back together and she runs like a top.

Even my 2006 2 cycle leaf blower that was fed some true swill (3 year old mix then a tank of regular plus a dose of motor oil) still runs perfect with little attention.

The only thing I'm changing for this year for the 2 cycle stuff is what the Stihl dealer advised. Which was at the end of the season, use a can of TruFuel (or MotoMix) after running them dry. Seemed to make sense since those carbs are small and are corrosion prone. Not really a fan of the fuel and it's expense but $6 a season is fine by me.

 

[KenO]

Originally Posted By: RobertISaar
if evaporation left behind significant deposits, perhaps cut fuel flow and let the engine drain the bowl before putting it away?



I've thought of doing this as well. My old mower's carb really self destructed after leaving fuel in it over the winter.