Topic: Beauty is only skin deep! barnacles inside the tank CB350F.

[Ozzybud]

I Just Took possession of this beautiful  1973 CB350F. Online Auction from another state.I even requested a picture of inside the Tank prior to bidding. I was told by the seller he would not be near the bike until auction end. "rest assured there are no coatings only metal. I am not sure Ferrous Oxide(Rust) is still metal.

The Bike has 7750 miles on the clock and it appears to be correct. bright work is great . Minimal Pitting or corrosion. original paint on tank and side covers are stunning. It runs smooth as silk, idles great an pulls hard to red line.

Sad that this what happens to a low mileage bike that likely sat for years with little or no fuel.

Looking for suggestion on cleaning the inside of the tank without using anything corrosives that can harm the paint?
Does diesel fuel and a handful of small nuts and bolts then shaking work?

[Pbeattie89]

It does the job. Most of the rust looks loose, so the agitation should work well. Vinegar also works well and is very mild. If it gets on the paint, just rinse with water and baking soda.

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[Pbeattie89]

Beautiful looking bike btw.

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[Rayzerman]

I have used EvapORust, it's mild but gets the job done.  Fill the tank and let it sit for at least a day.  You can use your nuts and bolts also, likely needs a wee scrub after the soak.

[jonda500]

The way it was described to me you put the nuts & small bolts into the tank dry and agitate, then shake out the nuts & bolts, blow out the dust with compressed air and then rinse out with diesel.
For an even more thorough clean (but still without using any acid or water) use natural colored aquarium gravel instead of nuts & bolts and agitate by wrapping the tank up in underfelt, bubble wrap or similar and leave it in the clothes dryer for a few hours (fluff cycle no heat!). P.S. Don't use gravel in the later style tank with the flap and recessed filler as it is near impossible to get it out! Bicycle chains are good in these or a magnet on a stick to retrieve the nuts and bolts.
John

[JustCruising]

I made the mistake of using muriatic acid once, ended up with a paint shaped tank with almost no metal behind it. Oops....

[Stev-o]

+1...EvaporRust. I bought it at Summit...

https://www.summitracing.com/parts/sum-er018?seid=srese1&ppckw=pmax-oils-fluids-sealer&gclid=Cj0KCQjwsJO4BhDoARIsADDv4vAiGxAe_rwZ6KFTGEkaS_E30G9vV-vA-gWthqOKAJTJdNJa2eJuxf0aAqRrEALw_wcB

[MauiK3]

They also sell more potent cleaning vinegar here that works well, is a bit faster but you have to keep an eye on it, it's potent.

[jakec]

A WAY better method than nuts and bolts in my experience is to use about 2 feet of medium sized chain. It does the same job but it's much heavier and as you slowly move the tank around it also covers a much larger area. I would soak with phosphic acid or metal rescue for about a week then use the chain. I did this on my K0 tank and it came out spotless.

To be more specific, remove whatever chemical you've had soaking. Then add the chain and a few cups of water and roll it around slowly and gently. The water is to catch the particles and make them easier to dump out. Pull out the chain gently and dump the water. Rinse some fresh water and dump it, then repeat the process.

The chain is easier to remove by just grabbing a link with something and pulling the whole thing out. When I did my tank this way recently I did about 4 rounds with the chain and then dried with a heat gun. In all it took about an hour including setup (not counting the time soaking with chemicals).

[Kelly E]

We have done over a dozen tanks with EvapoRust with great success. We buy a 5 gallon bucket and fill the tank all the way up. It works best warm if your shop is heated. We let it soak for a week and then drain it back into the bucket through a paint filter in a funnel so we can inspect the tank.
If the tank is clean we rinse with diesel not water. Pour in a gallon and shake well, pour into a an old water/milk jug so you can see the sludge settle. Then pour back in the tank for another round and dump the sludge. Do this several times until you are happy then drain it well.
The diesel prevents flash rust and will not hurt a thing when you fill up with gas.

The EvapoRust will clean several tanks and a bunch of parts before it stops working. I've also derusted the outside of an intact but a little rusty stock 70' CB 450 DOHC exhaust. The carbon inside will ruin the EvapoRust so no dunking. I used a couple soft brass brushes and a 3' long plastic planter box. I poured a bunch of EvapoRust in the box and laid the pipe over it and started scrubbing while constantly dipping the brush. It turned out pretty good and the buyer was really happy with the stock exhaust.

[calj737]

If you happen to choose to use nuts and bolts with the de-rusting, use only stainless. Standard carbon steel nuts and bolts will be heavily affected by acids and counter your efforts.

Evaporust is paint safe, reusable, and well worth having a 5 gallon bucket of in the shop.

[rotortiller]

I made the mistake of using muriatic acid once, ended up with a paint shaped tank with almost no metal behind it. Oops....

I have used it with very good results, it's like any tool in that it has to be used correctly. The nice thing is even diluted you do not have to wait long for results before neutralizing. Kind of like working with fast cure epoxy, a good plan needs to be made.

[Adam80]

Evaporust works well and I would imagine works also well with a chain and agitator. The trick as mentioned is you have to buy enough to completely fill the tank and leave it for many days. It is very expensive stuff in some places so may not be ideal. You cannot feasibly in my opinion buy a half tank and rotate the tank as you will likely have many issues like I did (leaks out the cap, re-rusting while the opposite side is not covered etc).

The issue I found though, and this was with both vinegar and evaporust, is if the tank is degraded considerably like yours, the rust will quickly return even if using diesel etc. I resorted to using Caswell epoxy tank sealer after de-rusting that has so far worked well but cannot speak for its long term durablity. 

The best results I have heard of are people using concrete mixers/dryers/external agitators with internal abrasives like stones/chain etc.

[jonda500]

The issue I found though, and this was with both vinegar and evaporust, is if the tank is degraded considerably like yours, the rust will quickly return even if using diesel etc. I resorted to using Caswell epoxy tank sealer after de-rusting that has so far worked well but cannot speak for its long term durability. 

The best results I have heard of are people using concrete mixers/dryers/external agitators with internal abrasives like stones/chain etc.

+1 from me, I never put any water based liquids in a petrol tank! It's too hard to dry out the seams properly.
John

[rotortiller]

It's too hard to dry out the seams properly.

   

Try sloshing around pure alcohol or better yet MEK after dumping the water. Water is pulled into the liquid from the seams, use a hair dryer after you dump the liquid. Do it twice is your are anal lol.

[calj737]

MEK will immediately damage the paint if you spill the least amount of it. I’d discourage its use unless you are fully committed to a repaint. Most of the suggestions endanger the paint except EvapoRust, hence the best recommendation for rust removal. A liner may be necessary afterwards regardless of the method used.

[rotortiller]

Yes MEK needs to be used with care but methanol will be fine for sloppy people.

[Kelly E]

We've never had a tank flash rust after doing the diesel rinse. You need to rinse the tank at least 4 or more times to get rid of the EvapoRust, do a thorough job of shaking the tank every time and dump immediately. We've also never had to use a tank liner afterwards either. The EvapoRust will still be good after cleaning up a tank. If you degrease the parts before you put them in the EvapoRust it lasts a long time. One 5 gallon bucket will do the tank and all of the rusty hardware on 4 to 5 bike projects at least.

The current bucket has done 4 projects and is currently cleaning up lots of the rusty parts and hardware on the 01' Honda TRX 350 Rancher. You can play around with backyard solutions trying to save a couple of bucks all day long but I would rather do it right the first time. It takes a little time to work and we work on other parts of the project while it's working.
It's like spending thousands on your bike and then buying the cheapest tires you can find, it makes no sense.

[jonda500]

I remove rust by soaking items in molasses dissolved in warm water - then scrub the rust and molasses off with water - then immediately dry because the flash rust starts within seconds! I don't know how molasses attacks and loosens rust but it does it well and safely without eating the good metal,
John

[Ozzybud]

Thanks everybody for all the great suggestions. I am Just received a 5 gallon bucket of Evaporust. Then i am going to rinse with diesel multiple times to get all the Evaporust out. It is water based so the sludge and water molecules will settle at the bottom after each drain and then only take the good diesel from the top of the catch bucket and re use. It had an ounce or so of water in the tank when i bought  it.I drained The stinky gas out and put fresh non-Ethanol fuel in it, checked the strainer and it was clear. also drained the float bowls. I have put almost 100 miles on it since i got it on Sunday! This Bike is so fun to ride and runs amazing.
I will be cleaning The tank in a month or so when it starts raining. I am having too much fun riding the new Toy!
Of course I will not be running it on the reserve position!

[Rayzerman]

Isopropanol will absorb tons of water, so I'd rinse the tank with that first... then you can use your diesel fuel after that.  Or naptha will work too.

[Stev-o]

We've never had a tank flash rust after doing the diesel rinse.

Thx for all the good info, Kelly.  I have a Kawasaki tank to do. What do you use to plug the petcock bung?

[Kelly E]

We've never had a tank flash rust after doing the diesel rinse.

Thx for all the good info, Kelly.  I have a Kawasaki tank to do. What do you use to plug the petcock bung?

I leave the petcock on, the EvapoRust won't hurt it.

[Stev-o]

We've never had a tank flash rust after doing the diesel rinse.

Thx for all the good info, Kelly.  I have a Kawasaki tank to do. What do you use to plug the petcock bung?

I leave the petcock on, the EvapoRust won't hurt it.

The petcock leaks but I have a new one, but really dont want to expose it to that.  Was going to find a proper size rubber plumbing plug from Ace.

[Ozzybud]

We've never had a tank flash rust after doing the diesel rinse.

Thx for all the good info, Kelly.  I have a Kawasaki tank to do. What do you use to plug the petcock bung?

I leave the petcock on, the EvapoRust won't hurt it.

The petcock leaks but I have a new one, but really dont want to expose it to that.  Was going to find a proper size rubber plumbing plug from Ace.

It seems the CB350F does not have the standard protruding bung. It has 2 screws and an oval opening sealed with an o ring.  I guess I have to make a block off plate..