Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Spenny62 on March 14, 2019, 02:01:21 PM
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I'm having a few problems with dirty fuel and think the tank has rusted inside with standing (there's no sign of the tank having perished). It has had a good clean out with caustic soda and well rinsed after but it seems that there's still rust inside which is getting into the carbs and now clogging up the inline filter I've fitted.
I've already had the tank sprayed so don't really want to buy a replacement.
What are my alternatives?
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If it's a 400/4 tank, its got a big long filter in the tank attached to the petcock. Maybe the caustic soda had destroyed this filter, so any crud would be going straight in to the inline filter you have fitted. Another option is to fill the tank with pea gravel and soapy water, or similar, and shake like hell to help remove more of the rust.
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empty tank. Really very empty. insert pea gravel as above^^. wrap in duvet. insert package to tumble dryer. 20 mins on the ambient setting (*no heat!) and you're clean.
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Ive had various tanks with that problem- bits in fuel.
I had a brace of Mobylettes a while back and used CITRIC ACID and sealer.(Moby's have integral frame and tank, so wont fit in a tumble-dryer!!)
My present tank has a sealer applied- which has come away in lumps- looks like bits of gel-coat.
Anyway, ive cleaned out what I can and fitted an inline fuel-filer- its been like that for about 5 years now with no further issues except a leaking inline filter- which i replaced.
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Caustic is the wrong thing to clean a tank out with, ideally you should pickle it with a solution of 10/15% sulphuric acid and a piece of stainless chain mail, seal it up shake around for a good half an hour,empty and wash through with lots of D.I water, dry quickly and apply some WD40, then make sure you have the internal filter in the tank and preferably an inline filter too.
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My petcock after many years...
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Filter looks like it's working!
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I have used the electrolyte method in the past with great success... remove petcock, seal the remaining hole, fill with electrolyte to the brim, suspend a metal coathanger or similar in the filling hole isolated from the tank with a plastic cap (make a hole in the cap and push the top of the hanger through it) this will be the sacrificial anode. Connect the positive lead of a battery charger to the part of the anode poking out of the top of the cap and the negative to the tank itself (a bared area of metal on the tank). Keep an eye on it at first to make sure it isnt shorting, it should be ok with just a bit of fizzing.... leave it for a few hours, you may use up a couple of anodes... the rust will migrate from the tank to the anodes... keep going till the rust has gone It works! You will be amazed at the amount of crap that builds up on the anode... Lots of detailed advice on the internet.
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The tank has to be the sacrificial anode, otherwise you are plating the rubbish to the tank.
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I gave up because it simply went rusty again. I got a new tank and fittings from David Silvers. I had trouble fitting it at first and they tried it out for themselves and found out that it was a bit narrower at the fitting arches. I and anyone else had to reduce the size of the mounting rubbers so it would slide on.
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Spirit of Salts or brick acid , I use SOS cleans it so well you need to add in caustic soda to neutralise the acid or it gets covered in surface rust instantly . Once the caustic is out then rinse with water , add in petrol/ oil mix. Best bit its quick , couple of hours tops and cheap £3 for 500ml is more than enough for one tank.
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Spirit of Salts or brick acid , I use SOS cleans it so well you need to add in caustic soda to neutralise the acid or it gets covered in surface rust instantly . Once the caustic is out then rinse with water , add in petrol/ oil mix. Best bit its quick , couple of hours tops and cheap £3 for 500ml is more than enough for one tank.
By applying caustic to the acids you make it harder to rinse out quickly, D.I water is whats needed and plenty of it, if we had added caustic at this stage of the process on our plating line we would have so much contamination we would of failed every time.
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The tank has to be the sacrificial anode, otherwise you are plating the rubbish to the tank.
http://www.secondchancegarage.com/public4/gas-tank-cleaning-1.cfm
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Herein lies the problem for us newbies who need to de-rust a tank for the first time - so much conflicting info everywhere... :-\
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Herein lies the problem for us newbies who need to de-rust a tank for the first time - so much conflicting info everywhere... :-\
No false info here, i am a former plater and metal chemist, the best way to do this at home is brick cleaner and a handful of pea shingle, seal tank, agitate, drain and rinse with loads of D.I water, the DI water is important, then dry quickly and swill with WD 40, i buy it in 5litre cans, no twatting around with aerosol cans, trying electrolysis is hit and miss at home due to lack of the correct equipment and knowledge.
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Electrolysis at home is a piece of piss as long as you adopt the correct method...there are hundreds of descriptions on the internet all describing the same technique..12v battery charger (everybody has one) connect positive to metal wire suspended in tank (metal coathanger will do), negative to tank as described. I used “arm and hammer” soda crystals to make the electrolyte as they are often recommended. It works very well. As with all forums, you have to do a certain amount of filtring. My suggestion of the electrolyte method is merely a suggestion, others will suggest other techniques i.e acids etc.... But the technique I described is correct, you dont need to be an “expert”, just connect it up the right way round.
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Like i said incorrect equipment and lack of knowledge.
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I rest my case. Kevski, to be clear, I said "conflicting"; I did not imply, or state outright, that any of your info is false.
I'm not saying that having all these different options is a bad thing. Everyone obviously has their own ideas of what's best; it just makes it a challenge for someone like me to decide how to proceed. No matter which method I choose, if the result isn't perfect, or nearly so, I'll second guess not only my execution of the process, but also my choice of processes...
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Well Matt, either kev’s right and everybody else who uses this technique is wrong and it doesn’t work....or its the other way round... you decide :)
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Well Matt, either kev’s right and everybody else who uses this technique is wrong and it doesn’t work....or its the other way round... you decide :)
Its not about right or wrong, its about correctly, i done this stuff for a living not as part of a hobby and that's where the difference lies, i offer suggestions based on what you might have kicking around in shed, i will also let you know the correct way it's done, but ultimately i don't have rusty tanks in any of my vehicles.
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Wouldn't making the tank itself the sacrificial anode ultimately weaken the tank?
Only if you plate out too long or the tank is done in to start with also the rust is already weakening the tank, what you are doing is taking the crap away from the tank and depositing it on the cathode, in the industry you clean using hot solvent or caustic based solutions and then it's D.I rinsed, then pickled with a 5/10% sulphuric acid rinsed again with D.I then plate up, timings are crucial,this is just a brief look at the process, naturally with tanks after the final rinse you need to dry it out quick and put protective coatings inside.
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I understand it as kevski states.
The steel tank that has rust is already compromised, or beginning to be, dependant on how much rust.
From a metallurgy point of view, steel sheet has been rolled to get it's thickness to required dimension for component pressing. This makes it effectively close to forged and maintains a compression of the surface that is a little resistant to corrosion because of its physical structure. It's this property that fuel tanks have taken advantage of for years, so they've never really been treated during production.
If you've left a piece of sheet that's been cut in damp conditions, the cut edges will very quickly corrode and general surface take much longer.
Once you cut, grind, corrode etc you loose this refined surface compression, making it far more likely to flash corrode as you further prepare it.
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Exactly ;D jesus! the poor guy only wants to know how to clean his tank..... i give up !
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Keep it simples.......pea shingle.
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Thought Jesus was more of a fish, wine and bread type of chap :) doubt if he studied metallurgy ;D
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I understand it as kevski states.
The steel tank that has rust is already compromised, or beginning to be, dependant on how much rust.
From a metallurgy point of view, steel sheet has been rolled to get it's thickness to required dimension for component pressing. This makes it effectively close to forged and maintains a compression of the surface that is a little resistant to corrosion because of its physical structure. It's this property that fuel tanks have taken advantage of for years, so they've never really been treated during production.
If you've left a piece of sheet that's been cut in damp conditions, the cut edges will very quickly corrode and general surface take much longer.
Once you cut, grind, corrode etc you loose this refined surface compression, making it far more likely to flash corrode as you further prepare it.
I started to read that and my brain said "Sod this, I'm going on holiday"
Can i come ;)
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My tank was rusty inside, I used DEOX-C to clean it before I liberally coated the inside with oil for storage. ;D
I had good results from (I don't have the pictures to hand). Not expensive, water soluble.
you can find it here https://www.bilthamber.com/corrosion-protection-and-rust-treatments/deox-c