Rusty tank.

[Mark]

Peering inside the tank I can see some surface rust.

Nothing dire or flaking, more a surface dust, the sort of thing you’d easily remove with a brass brush or similar, if of course you could get a brush in the tank.

I’m due to attempt to fire this bike up soon for the first time in decades and I’m wondering if a small in line filter would suffice, although as the fuel line gravity feed is so short that may not be too easy.

Then I wondered about swilling some rust converter around inside then flushing with water and leaving to dry. Or maybe swilling some sort of abrasive sand, beads or whatever around inside first, then using rust converter?

Lastly there’s the received wisdom of the sticky stuff poured in to line the inside which seems to split opinion re it’s effectiveness against modern fuel etc and associated even worse problems if it goes wrong.

Any ideas, proven solutions please?

Thanks,
Mark.

[EVguru]

Using fuel filters for a while is my usual approach. I'd never line a tank that wasn't leaking (fiberglass excepted).

Where I do want to remove, or at least reduce, rust. I've used the linked method with success.

https://web.archive.org/web/20181005035 ... moval.html

[harrymuffin]

In the goodold days it was accepted to use a handful of small ball bearings and gently skake the tank where the flaking rust was present. If you cannot 'dismantle' old bearing races then use of fine grit from recently resurfaced roads would do an equally good job - bit like sand blasting but more gentle. You would then rince out with Jizer and then hose the tank out 2-3 times untill water is clean. blow through with an airline and place in a warm environment - current sun would be perfect. You could of course simply turfin about 100mls of hydrochloric acid and let it settle where the rust is or if just surface rust swill it around being careful not to spill on your designer label clothes. The rusty bits will go grey then swill out with plenty of water until water is clean. Best to keep the tank full so no chance of condensation or if layed up drop an egg cup of oil in the tank and give it a swirl. Italien steel of this era was not very good quality, ask anyone who had a Lancia, the engines were prone to dropping out owing to rotting bulkheads, the wings usually rotted away bit like Vauxall Vivas and was a contibuting demise of Jenson when they bought a load of sheet metal from the Italians and wondered why the steel wings rotted away, leaving just the paint shell until you touched the paint case and the rust powder would then run out.

[3potjohn]

A leaking petrol tank saw off my beloved 6th gen Celica with a big jap can by way of silencer.I used to love it because when I pulled up people expected a chav (aka bogan in NZ) in to get out, but it was just an old git. Or was it?
I worship at the church of Por15 motorcycle tank repair kit from Frost UK. If you make sure the tank is dry Before the sealant goes in it will work.If it is in any way damp it won’t.

[Mark]

Thanks a lot for the replies, I’ve got a better idea now.
As the paint job is very recent and the rust minimal I’ll go for fuel filters In the first instance and see how it goes.
You’ve given me all the info I need if it comes to a more aggressive approach.
Frost U.K. look like an interesting retailer for people like us in general.
I know what you mean about Italian cars back in the day Harrymuffin - I had an Alfa Sprint, great fun,road holding, handling, speed etc, but at 6 years old with only 42,000 on the clock it dissolved into a pile of rust!

[George 350]

As a rust neutraliser, Phosphoric acid is much less hazardous than hydrochloric acid. It is available at 45% solutions easily and quite cheaply. Unlike hydrochloric, it won't (ok it will, but it will take absolutely ages to) eat through the 'good' steel in the tank. It is the active ingredient of 'Kurust' and other derusting products. A dilution to 20% is perfect for derusting, and should you spill it, provided you are quick to rinse off, it wont damage your paint. A rinse with a washing soda solution to neutralise any acid, blow dry and/or let it sunbathe as Harry auggests and you are good to go.
The leftover acid can either be quite safely poured away in the drains (it is sold as a draincleaner) or rebottled to use on derusting all kinds of things you will find to derust.

[Ming]

For surface rust I use cheap white vinegar. Fill the tank, leave to stand a day or two then empty back into the containers. Rinse well with some sodium bicarbonate in the water and that often does the trick. I've also used electrolysis for heavier rusting, and for leaking tanks 'Slosh' from rust.co.uk.

[72degrees]

I've had good results with POR15 (the Puch GP50 tank that was left empty in a greenhouse for a decade). For the Forgotten Error 125H tank that literally had pinholes from the outside and some interior surface rust, once the holes were filled, I got away with the nuts and fuel rattle method for the inside. I did fit in-line filters in both fuel lines though. I also have them on the road 2C/375. On that there is room to fit them, but they don't look very 'original' - then on a 'hybrid', that's not an issue

[SupermotoDave]

Remember there are Washable filters in the carbs.

[EVguru]

Remember there are Washable filters in the carbs.

There are strainers in the carbs. It's stretching the definition a bit to consider them filters.

[72degrees]

Remember there are Washable filters in the carbs.

True. The advantage of the stainless steel?/clear glass/plastic? ones fitted before the fuel gets that far is that you can quickly see if any clag is building up. On a single (electric) tap setup, just one might be a cunning temporary measure, so long as you don't go on to reserve. The downside, is that I'm not sure how easy to clean they are. The carb filter is pretty simple to, once you have got to it. Fortunately, my precautionary tactic has so far eliminated the necessity to do either, and I'm too idle to replace the fuel lines without them - well until they go brittle anyway

[Mark]

I think phosphoric acid is an ingredient in a lot of rust converters, so given it’s reduced propensity to ruin the almost new paintwork on my tank if spilled I would make it my second choice after in line filters.
Not sure if this is a dumb question but does it make any difference if the in line filter is vertical or horizontal on the line?

[EVguru]

Phosphoric acid converts Rust (hydrated Fe2O3) into Iron Phosphate (FePO4), which is chemically quite stable. Sheet steel is often Phosphated in raw form to discourage rusting.

[Ming]

I think phosphoric acid is an ingredient in a lot of rust converters, ...

Another 'cheopo' option is to use cheap supermarket cola instead of white vinegar. You can always strain it and offer it to guests afterwards...

[Mark]