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De-rusting (sort of) the petrol tank

Wagonwheels

Member
Joined
Jul 6, 2024
Total Posts
26
Total likes
19
Location
UK
I should know better, but......I decided to remove as much rust from my CB400N as I could. In the past I have used an epoxy coating, electrolysis and shake\rattle and roll with nuts and bolts...someone recommended Hydrochloric Acid...aka Brick or Muriatic Acid (bit drastic!)
With my smaller machines rust does not seem to be a problem (perhaps I should not have said that :unsure:).
So having watched even more Utube videos, I dived in....
I used white vinegar and it worked well, result! Emptied the tank of the orange gunge and filled with new fuel and drained through two filters, one in line and one in the filter funnel, several times finally filling the tank almost to the brim.
A fortnight later after sorting the carb leaks, I looked in the filler cap. Rust everywhere, looks worse than when I started. Back to square 1.

I should say the tank is off the bike and on a tressle while filling and flushing and kept in an unheated garage with the other bikes.

If anyone has been there and succeeded I'd appreciate any tips, meanwhile I'll order up some more white vinegar......

Many Thanks
 
I would personally stop using white vinegar. It will give good results at first, but the flash rust can be almost impossible to tame, at least in my experience.

Check out my results with Rust911. It’s non-acid based. The acid in the vinegar is what causes the strong flash rust. It has the same effect as evaporust, but cheaper. Hopefully you can find it in the UK.

Thread 'Rust911 Ultra-Concentrate Rust Removal'
https://www.vintagehondatwins.com/f...rust911-ultra-concentrate-rust-removal.10325/
 
Since you're in the UK look for Bilt Hamber Deox-C and Atom-Mac. Works really good
 
I should know better, but......I decided to remove as much rust from my CB400N as I could. In the past I have used an epoxy coating, electrolysis and shake\rattle and roll with nuts and bolts...someone recommended Hydrochloric Acid...aka Brick or Muriatic Acid (bit drastic!)
With my smaller machines rust does not seem to be a problem (perhaps I should not have said that :unsure:).
So having watched even more Utube videos, I dived in....
I used white vinegar and it worked well, result! Emptied the tank of the orange gunge and filled with new fuel and drained through two filters, one in line and one in the filter funnel, several times finally filling the tank almost to the brim.
A fortnight later after sorting the carb leaks, I looked in the filler cap. Rust everywhere, looks worse than when I started. Back to square 1.

I should say the tank is off the bike and on a tressle while filling and flushing and kept in an unheated garage with the other bikes.

If anyone has been there and succeeded I'd appreciate any tips, meanwhile I'll order up some more white vinegar......

Many Thanks
I cleaned my tank three times with "cleaning" vinegar and I've had very good results. I let the tank soak, full of vinegar, for two or three days each time. After flushing the tank a few times with water after the last soak, I blew in the tank with air pressure to remove as much water as possible, then used WD40 to soak the inside of the tank while it sat before I put it back on the bike. I did install a small filter inline and it seems to be catching any leftover particulate. So far I have close to 3000K on the bike and it is running fine. My tank sat for 37 years and it had a lot of rust and sludge in it.
Bobfilter steps.jpgfilter-2.jpgLine.jpgTank.jpgtank before.jpg
 
I have had great success with vinegar on several tanks. As others have mentioned, it is imperative to treat it ASAP afterwards to stave off the flash rust. I rinsed thoroughly with water, blew it out with compressed air, then dumped a cup or so of rubbing alcohol in to help dissipate any leftover water. Then I liberally coat it with my choice of penetrant fluid (currently using GIBBS Brand). I have heard of many others mixing up a batch of 2-stroke gas to slosh around. The oil mix in the gas keeps the flash rust at bay.
 
I wrote up the POR-15 process I used on my SL350 tank in this thread. I think I went into pretty good detail and included lots of pictures. Folks seem resistant to using POR-15. I think it does a terrific job, so long as you follow the directions.





Today, a friend and I rode our BMW R90/6 Airhead bikes on a 120-mile (round trip) lunch ride. As it happens, I stripped and lined the tanks on both of the bikes we rode today. I did them a little over 8 years ago. Both are still very clean inside. The coating has held up well. I am a firm believer in this product.
 
Ray I like that you coated the top rim area too. That is important IMO as the gas from the rubber cap seal can eventually get into the paint on the lower rim area and migrate over time into the tank finish
 
I cleaned my tank three times with "cleaning" vinegar and I've had very good results. I let the tank soak, full of vinegar, for two or three days each time. After flushing the tank a few times with water after the last soak, I blew in the tank with air pressure to remove as much water as possible, then used WD40 to soak the inside of the tank while it sat before I put it back on the bike. I did install a small filter inline and it seems to be catching any leftover particulate. So far I have close to 3000K on the bike and it is running fine. My tank sat for 37 years and it had a lot of rust and sludge in it.
BobView attachment 38112View attachment 38113View attachment 38114View attachment 38115View attachment 38116
Many Thanks for the information and method. Tank is now full of vinegar.... again! Daughter thinks I'm drinking the stuff! The photos help and look very familiar, I have replaced the tank filter with new (and shorter) and included a small inline filter (a lot of trial and error...and superglue!). Can't help feeling this has all been done before. Still wonder why there is only one outlet on the tank even my 1956 197cc Sun has two..... Thanks Again
 
By way of an update: So having filled the tank with white vinegar I then succumed to the seasonal sickness, flu. I had a COVID and a Flu jab two weeks before :rolleyes:. Anyway it put me out for a complete month and was petty bad. So when I finally got to the tank I was expecting the worst, rust running riot inside my tank......to my complete surprise the inside seemed rust free! The inside had a clean, but dull grey surface. Emptied and flushed tank, put some soda solution in to neutralise the vinegar, flushed again and sprayed as best I could with WD40. It now is half full with petrol waiting for warmer days.....
I understand that Thanksgiving is coming up next week, so hope those that celebrate have a great holiday :giggle:
 
I should know better, but......I decided to remove as much rust from my CB400N as I could. In the past I have used an epoxy coating, electrolysis and shake\rattle and roll with nuts and bolts...someone recommended Hydrochloric Acid...aka Brick or Muriatic Acid (bit drastic!)
With my smaller machines rust does not seem to be a problem (perhaps I should not have said that :unsure:).
So having watched even more Utube videos, I dived in....
I used white vinegar and it worked well, result! Emptied the tank of the orange gunge and filled with new fuel and drained through two filters, one in line and one in the filter funnel, several times finally filling the tank almost to the brim.
A fortnight later after sorting the carb leaks, I looked in the filler cap. Rust everywhere, looks worse than when I started. Back to square 1.

I should say the tank is off the bike and on a tressle while filling and flushing and kept in an unheated garage with the other bikes.

If anyone has been there and succeeded I'd appreciate any tips, meanwhile I'll order up some more white vinegar......

Many Thanks
Remove tank, take petcock and top filler off put one cup of BB's or pellets into tank, I've used small smooth pond pebbles from the pet store too, seal any openings with duct tape wrap tank with foam rubber or several large bath towels Pack into clothes dryer real tight so it won't move around, put dryer setting on fluff so no heat let it go for 30 minutes or more. Remove tank, remove BB's/pellets blow out tank with air hose rinse with a bit of fuel Tank will look new, no chemicals, no mess. Be sure not to tell your wife what you did with the dryer.
 
The POR treatment process works well, if done carefully, following instructions to the letter. I've done a couple of tanks with this stuff, oldest one 10 years back and still good.

A much cheaper solution is to use phosphoric acid, available on Amazon, used as toilet cleaner. Removes the rust and leaves a phosphated surface, which can then be lined ( I've used some UK based stuff called SLOSH ), or just used as it is, just rinse and dry, then add petrol.
 
Remove tank, take petcock and top filler off put one cup of BB's or pellets into tank, I've used small smooth pond pebbles from the pet store too, seal any openings with duct tape wrap tank with foam rubber or several large bath towels Pack into clothes dryer real tight so it won't move around, put dryer setting on fluff so no heat let it go for 30 minutes or more. Remove tank, remove BB's/pellets blow out tank with air hose rinse with a bit of fuel Tank will look new, no chemicals, no mess. Be sure not to tell your wife what you did with the dryer.
Many Thanks for the advice, I did wonder if the tank had baffles as not everything came out of the filler hole without some jiggling. Hopefully with some warmer weather progress can be made. For some reason lying on my back on a concrete floor during winter does not have the same appeal as it once did and so I’ll let the garage warm up a bit first……
 
Now that is a new approach! -Zen and the art of motorcycle maintenance- but I'm no Bob Pirsig although he did have a Honda. :unsure:
 
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