Rusted Tank

So I started a restore of my 82 GPz KZ750R . I already have ordered por 15 fuel tank stripper and sealer. I just am not sure how to prep the tank and take out the fuel gage assembly . I have already removed the bad gas, sludge, and most of the free floating rust in the tank. This is my first project on a bike and I am not wanting to damage anything.

Could use muratic acid for fast rust removal (leaves new flash rust) , followed by phosphoric acid to remove the flash rust, then rinse by sloshing with fresh gasoline (fast dumped through the open filler cap hole), and forget the sealer as the tank is then ready for action.

A quick water/soda rinse after dumping the muratic acid, and dousing with WD40, may suffice in lieu of the phosphoric acid.

Good Fortune!

The fuel gauge assembly is removed from the bottom of the tank...flip the tank over, pop off the plastic oblong cover gently with a flat screwdriver. You'll see six bolts...remove these and lift the fuel gauge out of the tank. If your tank has been really rusted and sludge-filled, then the gauge is probably shot. You can attempt to clean it up (but it doesn't disassemble) and see if it might still work...if not, they are NLA from Kawasaki, at which time you become one with the eBay Force. The fuel gauge assembly is the same for the 1982 GPz1100 and GPz750. Possibly other models but not other years of GPz's. The gasket that sits beneath the fuel gauge is still available from Kawasaki.

go take a look at por 15. i had it done to my tank an its great.

I took my tank down to the friendly neighborhood radiator shop. They boiled it out and red koted it for about $100. I've heard that a red koted tank can completely rust away but you'll be still be left with a tank made out of red kote.
Might be an exaggeration... but I would not risk a big buck paint job without the tank being red koted first.

Patton is correct - forget the sealer. It is not needed and will eventually fail and cause problems. The oxygen in water causes rust, so the object of the game is to prevent water from collecting in the tank. So, once the rust is all removed from the tank just keep the tank full of gasoline and it will not rust. My tank is 37 years old and it has no rust. Ed

The "Metal Prep" derusting solution sold by Por15 is phosphoric acid. Great stuff. You need to fashion some plugs for your tank then swish this stuff around inside until all the rust is gone. Don't be fooled by the suggestion that you can seal over rust. While that Por15 sealer/paint stuff is pretty amazing, sealing over rust is a suckers bet and not advised if long term success is the criteria. Another option is Metal Prep from Home Depot ($15/gallon) which is also phosphoric acid. Dump in the entire gallon and then shake and rotate the tank into various positions until all the rust is gone. This typically takes a few hours but actual time depends on how rusty the tank is.

After a good derusting you need to rinse the tank with water. Some light flash rust may form but it shouldn't be too bad since the phosphoric acid leaves behind a phosphate coating on the metal. Some alcohol in the tank after you get all the phosphate solution rinsed out will help dry the tank and protect against rusting.

Rust is like cancer so if the tank has heavy rust I'd go ahead and seal it over with the Por15 paint/sealer. Technique is everything with this stuff and you need to make sure 100% of the inside of the tank is coated otherwise rust will get underneath and the liner will subsequently fail.

Again, you need good seals for the various openings and then dump in the sealer. Rotate the tank though every possible angle, making sure you get the sealer to flow every which way. The frame backbone hump is particularly difficult to cover so focus your attention on getting the sealer to flow over this area. After you are confident the tank is covered, dump out the excess though the petcock hole. You will still have a goodly bit of excess sealer in the tank but this is okay. Keep rotating the tank proping it up in various angles to keep this material flowing over the surface until it kicks off and hardens (about 45 mins. or so). If you do it right you can get at least two good thick coats of material on the tank before it hardens up.

Good luck and hope this helps.

Thanks for the tip on the fuel gage assembly. I was just afraid to break anything haha

www.por15.com/POR-15-Motorcycle-Fuel-Tan...Repair-Kit_p_60.html

This is what I had already ordered it has everything I think I'll need to get the job done. The only thing I'm wondering is how to plug the bottom of the tank. I was thinking using the original gas cap fastened with a truck strap. I had to break it off since it had siezed shut. While the website says to use cork or duct tape, I'm not to sure about that for the bottom holes. I feel the duct tape shouldnt be too bad as long as it doesnt sit on it for a long period of time. I should be recieving the kit sometime between tuesday and friday of this week. So heres hoping that por 15 lives up to the hype

If you're trying to seal the holes on the bottom of the tank (where the petcock and maybe a fuel gauge sending unit were if so equipped) you can make a metal plate, put a gasket or piece of rubber between the plate and the tank, and use the original screws to tighten it in place so it doesn't leak. Ed