How much Evaporust?

[Knapdog]

I've just noticed this under the filler cap......







I've cleaned most of it off with a scourer but obviously can't get behind it....









Once I start thinking about fitting my Pingel I'll have tank off and stick an endoscope up inside to assess the rust situation.
It could, of course, just be around the filler cap area. Anyway, if treatment is needed I've decided to go down the Evaporust route.
This is not particularly cheap. I've already bought 5 litres for £34 and could get a batch of 20 litres for around £105.
The question I have is, do I need to bite the bullet and fill the tank right up with 20 litres of the stuff or could I get away with say 10 litres and periodically invert the tank?
Just wondering.  
Once I have emptied the Evaporust from the tank I presumably need to flush around with a hosepipe  Could I then just slosh fuel around to prevent flash rusting or do I need to completely dry out with a hair dryer first? Or are there better methods?
I have this picture in my head of flash rust appearing as soon as I add water.
Once Pingel is fitted the bike will be wintered until March with tank full of fuel (Ethanol Shield added).
Thank you.

[Valker]

I’d clean and coat it with Kreem fuel tank coating as per instructions. Save and filter the Evaporust as it can easily be reused.

[Knapdog]

I’d clean and coat it with Kreem fuel tank coating as per instructions. Save and filter the Evaporust as it can easily be reused.

Thank you but I just don't have any faith in coatings in tanks. I'm sure many would disagree with me but I've heard too many bad stories.

[Speedy Coop]

I have used the electrolysis method two times with excellent results. No paint damage and no coating afterwards, just keep it full of gas when you can. Google will give you all the info you need.

[luftkoph]

My bikes are laid up for winter 6 months out of the year, so this may not be a viable plan for you, but after you take care of your rust issues quickly put  maybe a liter or so of petrol in the tank and a liter or so of 2 stroke oil, slosh around turn upside down etc.

Every month or so I will pull the tanks off the shelf and give them a good shake

[Bagger John - #3785]

I’d clean and coat it with Kreem fuel tank coating as per instructions. Save and filter the Evaporust as it can easily be reused.

Don't use Kreem with a compromised (holed) tank.

Use POR-15 or the equivalent product which Harley uses as an OEM liner. Kreem is an invitation for moisture to wick into gaps between coating and tank, continuing the rust process.

You want something that absolutely and completely bonds to the base metal, after said metal has been chemically prepped to stop and reverse the oxidation reaction which is occurring.

[Bagger John - #3785]

My bikes are laid up for winter 6 months out of the year, so this may not be a viable plan for you, but after you take care of your rust issues quickly put  maybe a liter or so of petrol in the tank and a liter or so of 2 stroke oil, slosh around turn upside down etc.

Every month or so I will pull the tanks off the shelf and give them a good shake

I fill mine completely to the middle of the filler neck with fresh gas then add stabilizer. ANY exposed metal in a humid environment (such as foggy air from snow melt days) is an invitation for rust to form.

Remembering to remove and slosh is a guarantee that most people WON'T.

[Steel cowboy]

Try vinegar, it should eat up all the rust, and it’s a lot cheaper.

[Knapdog]

So what did Honda do to the inside of the tanks when they first fitted them?
Were they bare metal? Were they coated with a thin film of oil or what?
As I've said, I don't know what the tank situation is yet as I can only see what's around the filler cap. I presume there's more. I'd like to get rid of any rust with Evaporust or even vinegar (probably for a week) and then keep the tank filled with fuel as often as sensible.
My conundrum is whether I need to get the full 20 litres of Evaporust. Actually I think the answer will be "Yes".
My other concern is the dreaded Flash Rust so, once the Evaporust has been emptied out and the tank flushed with the hosepipe, what's the next step?
I don't have the knowledge/experience to risk "electrolysis" though asking my local bike shop if they would do it is an option.

[Valker]

Just my experience for what it's worth. I bought an old, neglected Valk a few years ago. The tank was rusted inside pretty badly. I tried the Vinegar thing with buying six gallons and filling it completely. I kept checking it and refilling it for a month. I saw lots of rust flakes when I'd drain it, but there was still plenty of rust in the tank after the month. I bought Evaporust and filter it when I'm done so I can stretch out the expense.

[Bagger John - #3785]

So what did Honda do to the inside of the tanks when they first fitted them?
Were they bare metal? Were they coated with a thin film of oil or what?

In production they were bare (stamped) and I don't recall any sort of metal treatment being used inside. The alloy is probably a little more "stainless" but not completely so.

Been that way forever with their tanks.

[steveB (VRCC UK)]

Have a look at www.biketankrepair.co.uk. They recently repaired cleaned and lined my tank. Their lining is ethanol proof many of the old style 2 packs are not. Unfortunately not a cheap option.

[GWS]

To answer your question directly, yes,you will need 20 liters of Evaporust. Fill the tank and let it sit for the recommended time. I slosh it around several times while waiting.

Drain it and, as mentioned above, filter it so you'll be able to use it on your next barn find.

Rinse out the Evaporust with a hose.

Now, stick an air compressor hose with a trigger nozzle into the filler neck and wrap a rag tightly around it. Blast away and push the remaining water out through the petcock opening. If you don't have a trigger nozzle yet, you'll thank me for this advice - you'll use it all the time.

Reassemble and immediately fill with gas to prevent flash rust.

[Skinhead]

Get this from amazon:

https://www.amazon.com/OXALIC-Crystals-Cleaning-Removal-Remover/dp/B0147GM7CQ/ref=sr_1_3?crid=3437FWBAVWZIJ&keywords=oxalic+acid&qid=1636235759&sprefix=oxa%2Caps%2C203&sr=8-3

Mix them with water and add to the tank, a cup pr two to 7 gals of water should be plenty.  Leave it sit for a day or two, dump it out and inspect the progress, if necessary pour it back in and repeat until clean.

I used it to remove the rust from a neglected valk I bought.  These Cobras had 700 miles on them.  Before


After




We used to use this to clean the Iron oxide off our cars paint when I worked in the foundry, doesn't harm paint.  Also removes rust stains from concrete and siding.

[Gryphon Rider]

I’ve used Evapo-Rust on small parts in an electrostatic cleaner to good effect. If I were you, I would remove the tank from the bike, put 10 litres of E-R in it, and let it sit for a couple of days, then turn the tank upside-down to work the top half for a couple of days, and repeat until the rust is gone. Rinse with water, drain it, then pour in a couple of bottles of gas line antifreeze, and slosh it around before draining it; it should absorb any remaining water. Then reinstall the tank and fill with gasoline and your favourite fuel stabilizer for the winter if it’s not going to be ridden for a few months.

And reuse the E-R on other parts. I don’t know I would even bother filtering it, but just let the particles settle out of it.

[Knapdog]

I’ve used Evapo-Rust on small parts in an electrostatic cleaner to good effect. If I were you, I would remove the tank from the bike, put 10 litres of E-R in it, and let it sit for a couple of days, then turn the tank upside-down to work the top half for a couple of days, and repeat until the rust is gone. Rinse with water, drain it, then pour in a couple of bottles of gas line antifreeze, and slosh it around before draining it; it should absorb any remaining water. Then reinstall the tank and fill with gasoline and your favourite fuel stabilizer for the winter if it’s not going to be ridden for a few months.

And reuse the E-R on other parts. I don’t know I would even bother filtering it, but just let the particles settle out of it.

Thank you very much.
I've also heard of swilling around with Methylated Spirits as apparently that also attracts water.

[Knapdog]

Just a couple more questions before I get around to the job...
Will it be safe to use the existing filler cap if I turn the tank upside down with Evaporust in it? If it's just the top part of the tank that has any rust then I'll only be putting 5 or 10 litres in with the tank inverted.
Also, will it be OK to probe inside with a borescope/endoscope once the tank is emptied of fuel?

[michaelyoung254]

I’d clean and coat it with Kreem fuel tank coating as per instructions. Save and filter the Evaporust as it can easily be reused.

Thank you but I just don't have any faith in coatings in tanks. I'm sure many would disagree with me but I've heard too many bad stories.

I don't trust them either. I had rust in my tank as well, but had it professionally repaired. They sand blast it inside and out and then coat the interior with a ceramic like coating and then bake it. Once and done so I'll never have to worry about it again.

[RustyValkry]

The tank on my bike had a lot of rust flakes in it.  I ended up using Evaporust.  I started with 2 gallons and noted that it was doing a great job so I got 3 more and filled it up.  I used rubber plugs in the holes and rotated the tank just to be sure.  I had the Evaporust in it for a few days, it was the last thing I did before the bike was complete.  I  drained the Evaporust, rinsed the tank out, blew it out with compressed air as best I could then remounted it and filled it with gas.

I decided, given what a PITA it was to remove, clean and remount the carbs I didn't want to risk clogging them again over the cost of Evaporust.  Besides, the high test vinegar I found in the hardware store was about the same cost as Evaporust.  I have the Evaporust in my shed for future use.  Here in the salted northeast I expect I'll have opportunities to use it going forward.

[Knapdog]

I've poured in 20 litres of Evaporust from the filler neck after plugging the two bottom outlets.
I would say there's room for another litre and do at some point I will be inverting the tank rather than swilling it around every hour.
I shall check the tank in the morning which will be around 14 hrs from filling up.
After probing around with an endoscope I'm pretty happy with what just appears to be very mild rust.
This is a '98 bike with 13,000 miles which isn't a lot so my guess is it was parked up a fair bit of the time.
I'll post further pics of the next stage....

[hueco]

Wow. Never knew this was a issue. Mine looks brand new.

[Cracker Jack]

Wow. Never knew this was a issue. Mine looks brand new.

Not an issue for you if it looks brand new.

[Knapdog]

After 48 hrs with a 12 hr tank turn over in between (only because I was about 500ml short) these are the results..













If you look at pic 4, by peering into the tank, you wouldn't think there was a problem.
Some parts are fine but I can see enough rust for me to continue the treatment.

[Knapdog]

Just for the record, this is the scenario after one week of Evaporust....
I then flushed the tank out with water and kept shaking it until there was little or no water in it.
I then swilled a litre of Methylated Spirits around,  drained and skilled a couple of litres of petrol.
Once drained I gave copious sprays of Fogging Oil from both orifices. The bluish pic you can see is a pic taken with Fogging Oil wafting around...





















Looking at the results I would have no qualms about recommending Evaporust though be prepared to wait a week.

[AZdougness]

Similarly to Valker I went with Vinegar first for a couple days to get the flakey rust out of it. Rinsed it with a garden hose, then went to ER.

Evaporust works like a charm, first hand experience also. Filled it up, put the cap on. Every morning and night I swooshed it around for a few days. Cleaned that thing out nice and purdy.

Rinse with a garden hose, and then put a heat gun into the main inlet on low heat and leave her in a "safe" area for a day.

Be careful of not clogging your vent line, which is why I went for the vinegar and flushing through the outlet on the bottom of the tank first. If you clog your vent you will need to get a different gas cap (750 Ace).

[mello dude]

So then .....fill up with white vinegar,  sit for a few days, then rinse with water, then refill with evaporust for near a week,  then, water rinse and immediate fill with gas?

What about early on,  add piece of chain first and shake the hooey out of it to break any surface rust loose?

-----My neighbor want me to do one his 70s Honda450 tank....it's nasty...

[F6BANGER]

Dont use a small diameter chain. I used white vinegar and a long thin chain I had laying around the house. The chain broke into a bunch of smaller lengths and wrapped around the vent line. Took a long time to get all pieces out.