Varnish in tank

[TeddyG]

Greetings all,

While looking over and fixing some things on a 74 750SF that I recently purchased, I noticed what appeared to be heavy rust deposits inside the tank. Fortunately I was advised not to use a rust remover and use apple cider vinegar. After a few fillings, it gradually removed what appears to be varnish, with a nice clean metal surface now showing.
Of course my next step will be to inspect the carbs that no doubt also have varnish deposits. I,ll order a gasket kit and refer to the Green Book, and hopefully only carb cleaner will be needed.

 

[chrisk]

Hmm, interesting

Yes, pulling the carbs apart is the next step. Buy a a hanging tank, and fire it up. Maybe the sludge hasn’t progressed to the carbs yet??

 

[Cccg]

Ultrasonic carb cleaner bath is the best way I have found with 1%; ct18 truck wash added to the de mineralised water water. Four cycles around 38c and it all comes up like new.
The carby cleaner sprays in Australia don't seem to do a a dumb thing.

 

[Vince]

I Like the one Nulon make, it takes the tarnish off the outside as well.

 

[TeddyG]

Hopefully spraying carb cleaner in the carbs will be sufficient, followed by ultrasonic if needed. Interestingly, when I drained the gas from the tank, it was clean and clear w/ no brown varnish. The apple cider vinegar has some sort of chemical reaction to attack the varnish. I'm glad the tank is OK since replacements are $$. I'll avoid using ethanol though it's hard to come by here.