The best way to clean and remove varnish in the fuel tank of a motorcycle using Sea Foam [SOLVED]

I have a motorcycle that has sat for 4 yrs with Sta-Bil in the fuel. I bought a new battery and it started right up and seems to run fine. I also noticed some crud in the gas tank and wondering if adding Sea Foam to the fuel would help clean everything? If so, will Sea Foam dissolve the tank crud? Will running everything through the carbs to clean them as well ?

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Jim D.
Jim D.
3 years ago

Hi Steve. I will expect any gasoline that sat in a motorcycle tank for 4 years to be very degraded, even if the engine starts and runs. The light ignition vapors are long gone and the remaining gasoline fluid has turned to a heavy combination of suspended gum and varnish. [Gum and varnish are outcomes of ‘UNstable’ fuel molecules – hence the need for a fuel stabilizer.] The crud you’re noticing is probably fuel varnish residue that will suspend in the old gas when disturbed by moving the motorcycle or vibration from running the engine. The old gas will smell like varnish! Here’s what I would do: Remove as much old fuel as you can knowing the varnish will sit at the bottom of the tank. [Don’t worry about the varnish…Sea Foam will liquefy the varnish.] Add a can of Sea Foam to the remaining fuel followed by a gallon of fresh fuel. The reason you want most of the old fuel out is to create a greater ratio of fresh fuel with highly volatile ignition vapor. [If you can’t remove some of the old gas, add the Sea Foam and new gas.] Start and run the engine for 8 minutes to allow the Sea Foam concentration to draw through the carburetor circuits. Shut off the engine and let the motorcycle sit over night or longer (2 to 3 days is better). After the long cleaning soak, add another gallon of fresh gas and run the engine for 5 to 8 minutes to heat up. Then take the motorcycle for a short spin to create more upper engine heat and compression. Much of the Sea Foam will remain in the tank and continue to clean as you go. At that point the fuel system and fuel passageways should be very clean!

DirkJ
DirkJ
1 year ago

Is the same treatment recommended for EFI motorcycle engine fuel tanks?

Conner Kranz
Admin
Conner Kranz
1 year ago
Reply to  DirkJ

Hi Dirk – yes, same treatment for EFI.

Ed K.
Ed K.
5 months ago

I have a motorcycle that set for quite some time and the tank is varnished. It is sticking to the side walls of the tank. What would you recommend to dissolving and cleaning this tank with?

Conner Kranz
Admin
Conner Kranz
4 months ago
Reply to  Ed K.

I’d use High Mileage Motor Treatment. Sea Foam Motor Treatment would work too. Just follow the description in Jim’s comment.