Old, old, old gas... how to clean varnished gas from gas tank???

I am restoring a 1970 Honda CT90. It ran fine when it was parked about 18 years ago, but unfortunately the gas was never drained from the tank. :thumbsup: Needless to say it has turned to a sludgy mess!! Any ideas for the best way to clean the tank. Also, the gas valve was in the "off" position do you think the little amount of gas left in the float bowl in the carb evaporated or also turned to the sludge mess??? And will the carb be cleanable without being removed and placed in a chem dip? Thanks for your help...


in a case like that where ever there was gas there is sludge. cleaning the carb is always part of getting an old bike to run anyway

Remove the tank; fill about a third full with lacquer thinner; add about a dozen hex nuts; shake thoroughly for a few minutes; rinse with acetone.

The nuts act as an aggregate to loosen the sludge. The acetone rinses the lacquer thinner's residue.

Count the nuts, be sure you dont leave on stuck in there!

Berryman's B12 is a good carb cleaner in spray form, also comes in liquid. Dont get it on paint or rubber!

Let it soak, shake it daily, let it soak on a different surface, repeat as necessary!

Robert :thumbsup:

dude you have to take the carb off, take it apart, and clean it thoroughly with B-12 or something similar.

The tank can be cleaned out as the previous guy said. That works! Check for rust in there too. If it's rusted badly I honestly don't know how to fix that.

Kreem it when its cleaned, if rusted

Robert :thumbsup:

be aware the kreem is only temporary.it will eventaully come off and then its a big mess.

if the tank is rusty,find a clean one. :thumbsup:


my little bro on my combat wombat last sunday. :thumbsup:


Now why did I know that you probably have 49 Hodakas......

BC :thumbsup:

Now why did I know that you probably have 49 Hodakas......

BC :awww:

its a sickness. :lol::thumbsup:

I am not familiar with the CT90 tank.

But heres what I did with the tank on my '87 TRX250. It had rusted so badly, from sitting empty, it had holes. A Honda replacement tank ran about $400.00, money I didnt have!

So I removed the tank, cut it into 4 pieces with a Sawzall, fiberglassed the inside of each piece, wrapping the glass about 2 inches over the cut edges to the exterior.

After it dried and I examined it extremely thoroughly for pinholes and repaired them, I sanded the glass on the exterior, placed the pieces together and glassed them in position.

I painted the tank with cheap black paint and put some fuel in. If there was a leak, the gas would wask off the paint and pinpoint the defect. There were only 2 pinholes!

I made these repairs 10 years ago, they are still holding up fine! Sure, I lost a little tank capacity, but it was well worth the savings. With the tank mostly hidden by plastic shrouds, it didnt have to look perfect, but could have with a little more time

If a replacement tank is too expensive or non-existent, maybe fiberglass is an option.

Robert :thumbsup:

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