Topic: Sludge removal?

[Teach]

I'm getting closer to the end of my 1978 750F project and I've started work on the body pieces.  The tank I'm gonna use is off my parts bike (the original one is too nice to repaint) and has not run since the early 90's.  I emptied the 15 year old gas from the tank and rinsed it several times; some with plain water and some with CLR.  I've used a chain to loosen most of the big chunks.  There's still a layer of sludge in the bottom of the tank that's the consistency of clay.  I've been able to scrape some of it out with a screwdriver, but I'm not able to get to most areas of the tank using this method. 

So, I guess the question is: what can I use to get rid of this sludge that's a combination of rust and old gas?  I filled the tank with straight mineral spirits and I'm gonna leave it in overnight...it hadn't made much difference after a couple of hours.  I'm thinking about getting some Yamaha carb cleaner after seeing how well it worked on my carbs.  I have a Kreem tank lining kit waiting at the ready once I get most of the bad stuff out, and I'm not all too concerned with light surface rust.  What do you guys suggest?  Kerosene?  Some acid of some sort?

Thanks in advance!

[bhassell]

I had similar sludge in my 78 that sat for 20 years...
I plugged Petcock, and used about a cup of lacquer thinner, and a one pound box of 3/8" nuts to melt the sludge.  Took several days and lots of agitation .  Each day, drained thinner and repeated process.  Final rinse with fresh thinner to determine when completely clean. 

Did not harm paint but I took lots of care not to get sloppy when draining and filling too.  After I finally got the sludge out had a rust to deal with.  Used a Phophoric Acid cleaner from Home Depot Pain dept. and was well pleased with final results.  Bob

[Bob Wessner]

The Home Depot product, The Must for Rust, was mentioned in an earlier thread. Based on the recommendation, I tried some. See the before/after pics at;

http://www.sohc4.us/forums/index.php?topic=6437.msg58343#msg58343

[bhassell]

I could not find The Must for Rust in my Home Depot, I used a product from Klean Strip called Phosphoric Plus.  Both contain Phosphoric Acid and likely very little difference in performance.  Best of luck with your Tank! 

[Bob Wessner]

Not wedded to any brand either. The key as you mention is the phosphoric acid rather than some other.