Modern Vespa

I've been trying to prep my gas tank to coat it. They say to have the tank free of rust, oils, degreasers, water, etc. every time I go through the process, once I get to the rinsing stage, before the water can even evaporate the whole inside of the tank is covered in a fine surface rust.

I've tried rust removers like naval jelly, Apple cider vinegar, you name it. Same result every time.

I don't know what else to do...

Any ideas?

Don't coat it. Fill it with gas and keep it filled with gas.

Look, those formulas for tank coatings din't take into considerations all the different formulations/additives gas will have today or in the near future.

Think of it this way:
If the coating fails, then what?

I'm only resorting to having it coated because I'm at my wits end. I have been keeping gas in it since the first time I cleaned it. Somehow it's still causing problems. I'm tired of breaking down on the side of the road and pushing it home only to find crud in the carburetor.

I don't know what other option there is.

After cleaning, I put a little Ospho in it, shake it around to coat the whole inside and pour out the rest. When it is dry, I rinse it with a little gas and again pour out to make sure nothing crawled in there that will clog up the line. Works for me.

How did you clean it? I'm thinking about the possibility that there's still some thick rust caked in there where you can't see it. Maybe that 'whole inside of the tank is covered in a fine surface rust.' could be residue from said hidden rust? If so, chemical cleaning alone won't do it, you need vigorous mechanical action.

Find a dental mirror and give a look. I had a REALLY rusty tank and filled it w/ detergent and water with nuts and bolts plus a handful of coarse sand. Got it clean and rust free with no dirty gas problems after a year and a half. If really rusty and you want it clean I don't think shaking by hand will do it.

Try this: Suspend it from some bungees and connect some kind of big vibrator to it(OK, just use your imagination. ) I use a rod connected to a vibratory finisher.* Make sure you do FOUR cycles - upright, left side up, right side up and upside down. Rinse w/ hot water. Blow dry w/ a hair dryer & shoot in a little WD40 if you want some protection before you get the tap installed & get gas in it.

Now hang the tank up overhead and test everything. Run a whole tank of gas thru your tap(& its filter) and run the last of it into a glass jar. See any rust or other crud?


* look here for a good alternative to a vibrator if you wanna get some exercise or have energetic kids.

I've done the nuts and bolts bit about four times now. I've used naval jelly, phosphorus acid and cider vinegar(seemed to work the best) each time when I'm done rinsing with degreaser and water, inside looks silver, shiny and clean, but before the water dries the whole inside is covered in a fine orange rust. Very frustrating.

I guess I'm just going to keep at it and hope it eventually stops.

Vo0doo, I posted this before on cleaning the tank, basically nuts and bolts in the tank with the tap out, duct tape openings, wrap in a moving blanket, toss in the dryer(with no heat of course). After an hour or so, that's when I do the rest. I just use the Ospho to neutralize any rust in the top seam where the bolts and nuts may not clean it well.

Maggs, coating the tank is not the only way to cure a common problem with carb crud and is total overkill.

the use of a sintered in-line fuel filter is far more fitting for your situation.

http://www.mowersupplyusa.com/SLIM-LINE-FUEL-FILTER-14-SINTERED-BRONZE-SCREEN-Sold-in-5s-Priced-Individually_p_23286.html

i use them on my triumphs

I was reading the Ospho website. It says "A dry, powdery, grayish-white surface usually develops; this is normal - brush off any loose powder before paint application."

What about the "powdery" residue? I've always heard inline filters were a bad idea on Vespas...

What you have is flash rust forming as the water evaporates from very clean steel. Google "flash rust tank" to learn about it.

If it was me, I'd do the rust treatment again with the cider viniger, quickly rinse with water (don't wait for it to dry), then rinse with alcohol (water will be carried away with it), then rinse with fuel/2t mix and leave it full.

Good luck.

Thats total rubbish. They maybe unnecessary on most vespas but yours sounds like a keen contender for one.
Placed in front of the cylinder as it leaves the frame would be a good place for it.


The powder is zinc phosphate

The PO of my bike put one on after getting a couple tanks of shitty gas (never get gas while the truck is at the station filling tanks, it stirs up the sediment) and I've never had an issue and am too lazy to take it off. In your case I'm thinking it might be a good move. Humid Texas must be a bitch with rust.

The humidity is a bitch!

I'm going to try the alcohol. Wil denatured alcohol work?

I mentioned the Ospho because it will convert any rust left behind (like in the seams). On bare metal it will give it a slight etch but keep it from rusting. I rinse the residue on the surface away with gas, then fill it up. I lived most of my life in south Florida so I know all about humidity and salt air. Ain't fun.

On my GS tank, after bead blasting the inside I gave it another rinse with evaporust and then a rinse with water, then alcohol, and dried it with a heat gun. There was a very small amount of rust film but fuel and 2T put a quick stop to that.

Did my TV tank the same way 20 years ago and it's still fine.

You could skip the water and go straight to alcohol too.

...but what kind of alcohol. I mentioned denatured earlier because I happen to have some. Will it work, or would isopropyl be better...?

Big fan of scotch and bourbon here....er wait...,

Chemist wife suggest rubbing alcohol.

denatured has a small amount of oil in it as part of the denaturing process.

isopropyl would be a better bet. Do a test piece and see if it meets your needs

when i did my tank it was the nuts and bolts trick with water added..... empty it and rinse with water again till it ran clear then hit it with.... old petrol with some 2t in it...... had to wait about a week to get a new tap in so left it open and had no probs with rust.
I also run an inline filter and clear fuel lines have had no probs with crud in the carb

I think the cheapest denatured alcohol should be fine (here we call it methylated spirits). I'm guessing the isopropyl stuff would be expensive.

hope it works out for you....

I'm going with isopropyl since I've got a couple if bottles in the medicine cabinet. And I'll give the filter a shot too. Hopefully this will keep me on the road for more than a few hours.

I appreciate everyone's input.

The denatured alcohol has no water in it - it is pure alcohol. The isopropyl contains form 10 to 20 percent water.

And I don't know why you would need another filter. You usually have one in the tank and one in the carb float bowl area. But I guess it would not hurt.

I'm resorting to overkill.

The problem with an inline fuel filter in my experience is placement. If you put it under the tank its hard to get to. If it starts leaking, gets clogged, you have to take the tank out. There is no real way to get it outside of the body since the engine is so tight against it and it can restrict flow if it's shoved in.

Osopho is a great coating and works wonders on converting rust. Once its neutralised, washing it out with straight gas may do the trick.

Modern fuels contains ethanol, ethanol absorbs water (humidity in the air, condensation, etc). A non coated tank , even filled with fuel, will rust.

The sintered filter is a simple $5 fix and way superior to the mesh filters that are in the vespa. They strain smaller micron particles, are transparent and can be placed in an area where you can monitor the build up of crud coming from your tank and not into your carb. Seeing as he has the tank out already it makes for a reasonable fix . It would only restrict flow if the line were pinched. The filter itself will not restrict the flow. Theres a 90 degree angle one that might even fit inside the carb box, but there is just enough room for one in the area ive already suggested where the fuel line leaves the body. If it does need to be pulled off to be cleaned, its doing its job and the mesh one isnt. That may have to become part of your annual motorcycle maintenance, but so be it. Theres no harm in putting it under the tank and if you use decent fuel line and not that clear plastic brittle shit, with proper tightened hose clips it will not leak.
Ive had one on my triumphs for more than 10 years and not needed to pull it off to clean it because it got full, but thats not to say it wont happen, on the other hand i never need to blow out my jets, unlike vespas, and this forum is full of that symptom.


I agree, phosphoric acid is a decent product but the coating left is known to interfere with adhesion properties of polyurethane coating systems. Not that i suggest coating your tank Maggs.
SFvsr has a point, it is an irreversable proceedure and there are plenty of documented instances on different bike forums where the coating has failed ruining the tank. But then there must be a lot that also work well too i suppose.

With whatever path you go down Maggs, i wish you the best of luck.

This sounds similar to a problem I had years ago when wanting to refinish a cast aluminum alloy marine lower drive unit. If I stripped the metal down to bare aluminum atoms, once exposed to the air they were guaranteed to instantly form an invisible oxide layer that would prevent paint from permanently bonding. The proper technique was use some nasty chemical stripper before painting which would strip off the oxide and stabilze the Al with something else that the paint could bond to.

I don't know the answer with steel, but a proper machinist ought to know.

Others here though, say not to bother. My tank is about 8-10 years old, is not painted, and does not rust. I do not know if there's some kind of coating on it or not. Rust aside, our humidity here is very high most of the year and I got so tired of water problems in my carb I now always fill it up from a can after use and regularly keep an eye on water content in my tank and my storage can with a petro industry water detection paste. Maybe we just have crappy fuel quality I don't know, but so far, I've not had any other water issues.

If you do try isopropyl alcohol, be sure to get the sterilizing type 99%, not the rubbing type, which is only 70%, the rest being water.

P.S.
If I were serious about wanting to paint/seal the inside, I'd probably talk to a serious auto resto shop about it first to get their opinion/estimate.
I'd also probably search/post the question on vintage motorcycle/auto boards. There's a lot more of those out there than scooter boards and they often have members who aren't afraid to spend the $$ to get the best answers. You may find additional advice there. There's a lot of vintage petro engine tanks out there and you can't be the only one struggling with this issue.

Have i got this right? Clean, clear and flush the tank, then add Osopho, slosh it about, allow the Osopho to do it's thing, then flush again, dry the tank out, then add gas. ?

I have been thinking that i would need to have my tank 'professionally' cleaned and coated, because of the white 'salts' that build up on the roof of the tank and then clog up the filter, fuel line, and carb.

Is the Osopho route a tried and tested successful alternative to coating?

Also, i'm thinking that the 'salts' are not rust though, but a deposit left as a result of fuel reacting with the metal??


cheers

We'll I did the cider again and got a lot more sand-grain-sized chunks of rust out. I did it again until the cider ran clean. Then rinsed with water and alcohol and then rinsed over and over with about 2 gallons of premixed fuel, then sloshed some 2T oil all around to fight off the flash rust while I put it all back together.

I ordered a filter like the one linked to earlier in case I need it later(which it looks like I might)

I gave the carb a good going over (again) fired it up and it Ran ok as long as I gave it lots of throttle. It didn't want to idle at all with out jacking up the idle screw or giving it throttle. It eventually died and I had hell getting it to start again. It will run, but only with heavy throttle and then it will eventually conk out. Every time it dies it takes a while to get it started again. I guess I'm still getting crud somehow.

I don't know what else it could be.

The worst part of all of this is that before all of this started I had a one kick starter almost every time. Very frustrating.

Hi guys,
I didn't do this on a Vespa, but I used Metal Rescue on the tank of a CB750 k0 1969 that I was restoring. It took 24hrs on one side and 24hrs on the other side and it looked great. That stuff is not acid so the tank won't flash rust after. Actually, if you poor a bit of clean stuff back in and slush it around and let it dry, it will protect against rust for a year... after that, keep it as full of fuel as possible when stored and you should be ok.
I didn't want to coat it either...
I highly recommend it!
Cheers
David

my tank in my p200 is coated with some white stuff that the previous owner used. I still crud in my carb. I'm thinking of putting an inline filter on mine and my a better air filter.

I want to say something similar to this... http://www.jpcycles.com/product/352-055?utm_source=none&utm_term=adwords_labels%3DParts&device=c&network=g&matchtype=&gclid=CLWz8rbyg74CFWXl7AodExcAIA

I'm assuming you'd want to use protection when introducing this stuff to the tank.

Yeah. That and Red Kote seem to be the big names. Red Kote being the easiest to use. I really don't want to use either. I have a fear of the stuff failing and then I have a ruined tank. I don't want to lose my original tank with its original paint and patina.

Ive had a few tanks that I have bead blasted. When I get them home I rinse a few times with gasoline. After the gas rinse, I coat the inside with oil. This works for the week or so until I get the tank installed and fill it up with 2% mix. I have not had a tank rust up when I using this process.

To fix a rusty gas tank. Put nuts in a sock add water shack a little rinse. Then refill with an electro light solution of water and baking soda. Stick a piece of a coat hanger in the tank not letting it touch the tank. Hook a battery charger up one end to the coat hanger the other to the side of the gas tank. Let it sit a few days. When you shut things off the tank should be rust free. There may be a black oxide residue its in fact a harder type of rust and will do no harm more of a protective coating.