Topic: Strange Object in my Gas Tank ('74 CB750K4)

[Terry in Australia]

You'll need to remove all of the existing liner, as there'll be more rusty crap under it, and the new liner won't bond with it, so it has to go.

[Yoshimitsuu]

I thought of the same thing as when I drained the Metal Rescue it looked like it was mostly in one piece. However, after shooting some water into the tank with some weak water pressure some more pieces fell off. I don't really like the idea of having that stuff in my fuel so I've decided to test my luck with stripping it.

[ekpent]

 I used a paint stripper I used to use in my refinishing business to remove a Kreeme liner on an original paint K4 tank. It is real runny and water soluble for an easy rinse out. Other then that use MEK instead of acetone. Good luck as one has to be very very careful.

[ChopSticks]

You'll need to remove all of the existing liner, as there'll be more rusty crap under it, and the new liner won't bond with it, so it has to go.

Well that's the thing if the original lining is stopping leaks like some others have mentioned I wouldn't want to remove it. Also I'm fine with not adding / redoing the lining if I can get the rust out (that isn't covered by the lining) with the metal rescue without damaging the original lining

[carnivorous chicken]

While some are completely against lining tanks, I've relined a failed Kreem tank with Redkote and it has held for 4 years just fine. If you use acetone to get rid of the old liner (With a chain or something to shake in there), Redkote will mix with acetone and work just fine -- you can use acetone to thin Redkote. IMHO better to ensure you're not going to ruin your paint with an exposed pinhole leak, and just be careful with whatever you use to get rid of the old liner.

[Terry in Australia]

You'll need to remove all of the existing liner, as there'll be more rusty crap under it, and the new liner won't bond with it, so it has to go.

Well that's the thing if the original lining is stopping leaks like some others have mentioned I wouldn't want to remove it. Also I'm fine with not adding / redoing the lining if I can get the rust out (that isn't covered by the lining) with the metal rescue without damaging the original lining

The problem with that, is that once the old liner breaks up, fuel can (and will) seep between the liner and the tank. Once the old liner has started to fall apart, it needs to be removed completely.

Just to add to Larry's post, Be extremely careful if you decide to use MEK, the fumes can melt your eyeballs, it is a fantastic product, but probably the most dangerous solvent commercially available. Read the instructions, and don't splash it on anything you want to keep, including your own appendages.......

[ekpent]

 That old failing Kreeme always has rust underneath it that rust removers won't be able to get to. I got lucky on a GT550 tank once. It was failing and I had drained the gas much earlier and had let it set. I was able to get a hold of it through the filler neck and was amazed that I got it out all out in mostly one piece working and pulling carefully.Looked like a rusty deflated football when out. Of course the reason it released so easily is because the backside was completely covered in rust much like that little blob in your picture shows.

[ChopSticks]

I don't think the tank's lining has necessarily failed just that the PO didn't line the whole thing correctly so there are spots that have rust which are getting into the petcock/carbs. I want to remove that rust. I don't mind rust that is UNDER the liner as long as it's not leaking through and at the moment the tank has no leaks besides a faulty petcock.

Not sure if I got the answer yet, but if I use metal rescue it won't eat away at the liner correct? As long as I can get the current rust out I would prefer not to touch the liner.

[MoMo]

I seriously doubt Metal Rescue would dissolve the old liner

[RAFster122s]

You should be worried about the rust under the line.  It has trapped moisture and hear (outside in summer and using the bike give rust one of the things it loves.  Exposed bare metal infected with rust will only spread like cancer and actually work quicker to eat through the metal.  The metal cannot dry as it is trapped between the liner and the tank's rusty metal.

A failing liner once it starts never stops completely.  The fuel will wick under it where it has lifted a nd slowly increase the area it can reach.

SMe reason you do not paint over a paintjob where the paint is peeling, odds are it is only a matter of time before the rest goes.  Anything you do short of stripping it and redoing it is wasted time and money.

[madmtnmotors]

I don't mind rust that is UNDER the liner

You should. If rust is under the liner then the liner is not adhered to the tank at those locations. Only a matter of time...

[HondaMan]

I might try a gallon of lacquer thinner inside the tank (watch out for the paint!) to remove water and loosen the Kreem where it is sketchy, then dry it out and use the POR-15 process. This stuff seals everything, fully airtight, so if it is rust, it will stop where it is (no more oxygen will be available). The POR15 is also VERY hard, and has saved several tanks I had pinholes in, leaving a crust thicker than the tank afterward. Amazing stuff.
Not cheap.

[NobleHops]

Acetone will dissolve old style liners, including Kreem. Wrap the tank in shrink film, tape the filler neck as backup, use a gigantic funnel, and be careful. 3 gallons is plenty, move the tank around. Get a bucket and lid and save it. Get rid of that liner. You got this.

[Terry in Australia]

Yep, gotta get rid of that ol' liner before you can fix a tank properly.

[BRAD CHIEDUCH]

Kreeme liners should be avoided like the plague - absolute garbage.  I only use Red Kote and if you check with most radiator/gas tank shops this is all they use as well.