How to clean a cast iron gas tank

[BUDSVTX]

Picked up a Cushman Cub farm engine this weekend. Straight forward restoration, no surprises. Ignition is a Wico EK mag and it works, the usual stuck valves, piston is not stuck on this one, fuel mixer is very dirty, but the ultrasonic cleaner will take care of that. Biggest issue is how to clean the cast iron fuel tank, it is very heavy with a 1 1/4"NPT fuel spout and a 3/8"NPT drain plug and 1/8"NPT that goes to the fuel mixer. It is very rusty and appears to have had real gas left in the tank (black goo on the bottom of the tank). I am thinking of some kind of acid. Fill the tank to the top, let it sit for a few hours, drain and flush with water. Any ideas be appreciated.

Thank You

BUD

 

[BillK]

Do you have any radiator shops left in your area ? They will usually clean gas tanks also. Whatever chemical they use for radiators works great on fuel tanks too.

 

[gdocktor3]

I have a 1950s International Farmall 140 that sat for nearly 15 years until my father and I decided to get her running. The inside tank was covered with surface rust and pretty filthy. Basically we just pulled it off and filled it with simple green, swirled it around and drained it. Repeated with more simple green, then gasoline until the fuel came out clean. We replaced the fuel lines and filters, had the carb professional cleaned and rebuilt, then put it back together and it runs great. Not sure if this helps, but it worked for me.

 

[pcmeiners]

Oxalic based radiator cleaner or add lye and let sit for a couple days.

 

[gungatim]

for motorcycle tanks, muriatic acid works well but if the sheet metal is too rusty/thin you'll get pinholes. I am assuming with a CI tank, that Cushman motor is a hit and miss? all my Cushman's are in scooters so not familiar with the cub farm engine. at any rate, if the metal is decently thick, the muriatic acid should work well. just follow usual precautions with any acid.

 

[jakemac]

Fill it with white vinagar and let it sit for a few days then flush with water.
Dry it out (a hairdryer or heat gun should work) , then fill it about 1/4 full with course sand and shake and roll it to scoure the inside.
Flush it again to clean out all the sand.
You should be good to go.

 

[stercorarius]

If you are committed to getting it really clean really easy and have a little money, I would take it down to a local engine shop and see if they will hot tank it for you. I'm not sure what combination of chemicals they use. I've had them do a few engine blocks and cast manifolds that were in real bad shape this way and they came out great.

Sent from my S60 using Tapatalk

 

[BUDSVTX]

Fuel tank is really thick, would guess at least 1/4". It is bolted to the engine block and is used to bolt the engine to a skid or foundation. To remove it, I would have to pull one of the flywheels off, which is not a good idea. The flywheels are pressed on and don't have chinch bolts that tighten the hub of the flywheel to the crankshaft. Hot tank would be great if I could remove the tank. I usually use Kreme which is a 3 part tank repair kit that the motorcycle shop sells. This works great and I have done dozens of tanks without any issues. Because of the weight, I can't roll the tank to cover it with the plastic coating.

BUD