Grungy gas tank

rickfischer51

rickfischer51

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Joined
Jul 29, 2022
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I have 5 hp B&S flathead on my a tiller. Gas tank is gummy, varnished, but no rust. There is a plastic insert in the tank. Never seen this before. I've tried all kinds of stuff to clean it. Laquer thinner, acetone, denatured alcohol, etc., even a bit of the solvent in my carb cleaner bucket. No joy. If I take it in to get it boiled out, what happens to the plastic thingie? I assume thats a baffle to produce sloshing. Anybody run into this before?
 
It’s a plastic baffle to help with the sloshing.
I’ve seen a sponge inside there too. Bad idea because it deteriorates and clogs up the carburetor.
I would remove the tank, then I’d remove the baffle and clean the tank.
A replacement tank is about $100 last time I saw one.
 
Last edited:
andrewslarge said:
Here is a post from a few years ago about the baffle.

5HP Fuel Tank Problem


You might want to look for a Honda GC135, GC160 or a GC190 off a broken pressure washer. These usually have a plastic fuel tank and have the same bolt pattern as the Briggs 5HP.
Click to expand...
Look on FB at pressure washers with the Honda engines. I see one every once in awhile for FREE that has bad pump.

Also I've cleaned them tanks. Not a fun job . (if it's the type that cannot be replaced reasonable or vintage NLA) Easier way is to put some nut's/ screws inside, add plastic bag under the gas cap to seal the cleaner inside, usually just start with water, pad it good and tie/strap to a slow rotating tractor tire so as the liquid inside can be changed W/O removing the tank and just let it tumble. Go do other things.
Some will really surprise you how clean they get, (look inside with a flashlight) some will require a Red Kote or throw i away. Some replacement tanks cost more than the machine is worth, so go figure.

The Honda engines are really good, tanks do not rust and just a better all around engine as compared to the Briggs designs. (some of the Briggs gas tanks just turn to solid rust, not coated good and a waste of time)
 
Thanks for the replys. The chemicals I used did soften the varnish. I could get it out with makeshift brushes under the cap, but I cant get past the plastic insert. My insert is not foam. It is a rigid dark grey plastic. If I could get it out I could throw in some small nuts or something to break up the clumps. I have another tank, but the governer/carb linkages on the bracket under the tank are all different.
 
Just to help you. I have shortened the long fuel pickup to and put fuel line from a weed eater and a weed eater fuel filter on then end to rest at the bottom of the tank. The diaphragm fuel pump on the side has no issues and the cup at the top stays clean. Just an idea for you
 
andrewslarge said:
Just to help you. I have shortened the long fuel pickup to and put fuel line from a weed eater and a weed eater fuel filter on then end to rest at the bottom of the tank. The diaphragm fuel pump on the side has no issues and the cup at the top stays clean. Just an idea for you
Click to expand...
Some hints about the Briggs dual tube pulsa jet carbs
AND also if you keep the gas tank over 1/2 full the cup at the top for the short tube is using gas from the top of the tank.
The long tube is a pump pickup tube that pumps gas from the lower section of the tank up to the upper cup when the gas level gets low in the tank.

Hint: If the engine runs good with a full tank of gas but stalls or runs erratic with low gas tank levels the long PUMP tube is restricted or the carb diaphragm pump is weak. (the long tube pumps gas up to the upper cup reservoir for the short tube and the carb SUCKS gas up the short tube to the engine).Best to always on a cold engine to fill the tank for easier starts. (because the short tube is into immediate gas for engine prime and the long tube and pump is not involved)

link to carb info

Small Engine, Lawn Mower, Snowthrower Troubleshooting, Repairs and Safety

outdoorpowerinfo.com outdoorpowerinfo.com
 
is it a sludge or is it dried and caked varnish from dried fuel? Here is what Google AI says:

These chemicals work rapidly but must not be used on plastic tanks, as they can warp, melt, or dissolve certain polymers. [1]
  • Acetone: A highly aggressive, clear solvent that thins out and cuts through thick layers of gas tar. It evaporates incredibly fast, so keep the tank capped during the soaking phase.
  • Lacquer Thinner: A heavy-duty paint solvent that melts stubborn, dried-on gasoline crust. [1, 2, 3, 4, 5]

-----> Safest and Most Effective Solvents
These products will aggressively liquefy the gummy varnish without damaging the plastic material of your tank:
  • Berryman B-12 Chemtool (Liquid): This is the fastest-acting option for heavy buildup. It cuts through varnish rapidly but remains safe for standard mower tanks when used as a short-term soak.
  • Aerosol Carburetor Cleaner: Spray cans (like CRC or Gumout) are highly pressurized. The spray blast physically knocks loose varnish while the chemical dissolves it. [1]
  • Sea Foam Motor Treatment: The safest, gentlest option. Pour it into the tank undiluted and let it soak for 24 to 48 hours to melt the crust.
  • E85 Fuel: If you have a gas station nearby that sells E85, a few dollars' worth will clean the tank beautifully. The 85% ethanol content acts as a powerful, plastic-safe solvent.
 
Regular Acetone can do a lot damage to both other metal items and you as it gases off when exposed to the moisture in the air. I have had tools damaged in the area where Acetone was being used. And also have had my breath taken away by the fumes. Acetone also has to be neutralized after it done its job with water. Any ferrous metal must treated with oil or it will flash rust. Also don't get the Acetone on any aluminum items as it dissolve them quickly which is why I use it to aluminum transfer on steel crankshafts.

Now they do make a low fumes version but quite a bit slower at cleaning and I do mean slower.

Acetone will damage that plastic insert.

As for the tank availability if it is the 3 quart one it has been NLA for quite sometime after it went over $100 cost for the dealers. The only two solutions available is a tank liner liquid and replacement of the engine. Tank liner can only fix the main part of the tank and not the fuel bowl cup directly under the carburetor.
 
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