Safely clean inside gas tank.


New Member
78 CB125s

I have no problem running the bike, everything is working. Last winter I neglected the thing and didn't fill up the tank during storage. Well... it rusted. At least that's what I thought.

The interior was all brown speckled just like rust. Filled the whole thing with Evapo-Rust. No luck. The Evapo-Rust did absolutely nothing. Came out clear!

What I did notice though is this rust stuff is build up, i can peal it off in flakes. (under that stuff the tank is 100% clean!)

Now I'm completely lost. How do i get that crap our of the tank? and safely.

Take a look at the photo attached, I managed to poke around with a flat head and removed some. Please advise.


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That looks like varnished fuel and like goldy said try acetone or a thinner and let it soak, put a piece of old chain in it and shake it around then dump it out.
And make sure you’re running with a fuel filter (and carry spares along with any tool you need to swap them out)
With acetone will I hurt the paint? + do i need to completely fill the tank, that's 2.5 gallons acetone. Disposing of that stuff is another story.

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Shouldn't hurt the paint and you only need maybe 500 ml and you can move the tank around to let it soak on the different parts inside for like 10 mins a time then put the chain in and shake it.

Also to know if the acetone will remove the glaze you can use a rag on a stick soaked in it and rub a spot, if the stuff comes off use it, if it doesn't try something else.
Sounds good! Thank you. I will try acetone.

BTW. I found some MEK in the garage, wondering if I should attempt it with this. Otherwise if Acetone is safer I don't mind spending few bucks.
MEK is heavy duty. It will wreck paint on contact! I would try acetone, denatured alcohol, or mineral spirits, first.
Can’t afford to mess up paint. It’s in real good condition for a 40 year old bike.

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HOLY CRAP! I’m impressed with the results. Thank you guys for the tip!

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fuego said:
HOLY CRAP! I’m impressed with the results. Thank you guys for the tip!

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So what did you end up using?

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After and before attached. I just used acetone and a couple bolts/nuts.


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Good filter, keep it full of gas and most importantly, ride the snot out of it as often as you can.

Bikes like to be ridden and don't need all this Kreem/pampering BS. Just run them as they were intended to by the factory (but add a filter and carry a spare/tool needed to swap them out).
I agree that when you use fuel filters you should ride with spare(s) and a tool to change out. They can become clogged quickly when you have a tank that is compromised with rust and or liners.
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