Grungy gas tank

[ZKaren]

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?

I have used isopropyl alcohol or a fuel additive like Sea Foam. For stubborn varnish or sludge, add a handful of stainless steel ball bearings or rock salt and shake the tank vigorously to act as a gentle scrub. It worked for me but I did leave it soak for a day cleaned it out and repeated it until it was clean enough to use.

 

[rhkraft]

All this crude comes from gasoline evaporation, water in the tank, or both. Keep gasoline in the tank and use 10% alcohol auto gas. The alcohol in the gasoline absorbs any water and keep sludge from forming. I have a 35 year-old push mower with a Briggs engine and the tank is still clean and shiny inside. I do keep it in a shed out of the weather, but I never had to remove the carb for any work and it starts every spring within 2 or 3 pulls. I just change the oil and clean the air filter annually and put in a new spark plug every 5 years. After 30 years I had to buy new rear wheels for the mower deck.

 

[JT White]

Mix White Vinegar and add some Dawn Dish soap (don't load down, maybe 1/4 cup and let if set for a day or two. See if that helps. It won't hurt the tank.