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Discussion Starter #1
Hey crew,

I acquired a Shadow that has sat for the better part of a decade with a half tank of even older gas. Luckily, the tank's integrity is intact. Unfortunately, the interior of the fuel tank is rusted to the point that knuckle-sized chunks of rust are loose inside. I've tried rinsing the sediment out and reaching for the larger chunks with pliers but the tank's geometry is really prohibitive for removing this gunk. A few observations:
  • The outlet is not the lowest point in the tank. With the petcock and stem removed, I need to rock the tank back to front to drain it. Even then some fluid and most solids will remain in the tank.
  • The inlet has a collar extending into the tank. If I turn the tank upside down, some fluid and the majority of detritus will pool in the highest point of the tank.
  • The area directly beneath the inlet on the bottom of the tank is peaked such that rust chunks will settle out of my reach with pliers.
  • As a corollary to the above, the edges of the tank are deep and narrow relative to the "shallow" center, allowing fluid and sediment to accumulate out of sight.
Here's an image of a similar tank. The tank is oriented nose down and photographed from the bottom.
284695


Have any of you had experience with these oddly shaped fuel tanks? I found an OEM replacement fuel tank online but it costs as much as the bike itself and I'd like to keep the original. Short of taking a plasma cutter to it, I'm running out of options.
 

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1983 Honda vt750 Shadow
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Most of these modern bikes have a goofy shape to the fuel tank to fit over the backbone.
There are good ways of cleaning them out. Some guys use chemicals or vinegar, put nuts and bolts in them and agitate them to break out the rust. Electrolysis de-rusting works too.



 

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Discussion Starter #3
Most of these modern bikes have a goofy shape to the fuel tank to fit over the backbone.
There are good ways of cleaning them out. Some guys use chemicals or vinegar, put nuts and bolts in them and agitate them to break out the rust. Electrolysis de-rusting works too.



Thank you for the resources. The drywall screws and vinegar route looks most appealing. However, if I can't drain the tank of loose rust sediment now, I'm not sure how to recover the drywall screw media after agitating them in the tank. I'm hoping someone here has already experienced and overcome that hurdle.
 

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Sounds like what I just went through. I used a low pressure pressure washer to help break up the rust, then maxed out the tank with EvpoRust and let it sit for a day, drained it and repeat until it was rust free. As for the getting rust chunks out, I stood the tank up and put a water hose in it until I couldn't see rust coming out. But like you said, you have to shake and twist and so that crap to get the big stuff out. I used a syphon pump to get the rest of the fluid/small stuff out. Good luck, took me about 2 weeks to restore the tank

Sent from my SNE-LX3 using Tapatalk
 

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You could use smaller things like 1/4" to 3/8" nuts.Or BBs.
On a day your wife is gone wrap a blanket around the tank and put it in the clothes dryer. ?
 

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Sounds like what I just went through. I used a low pressure pressure washer to help break up the rust, then maxed out the tank with EvpoRust and let it sit for a day, drained it and repeat until it was rust free. As for the getting rust chunks out, I stood the tank up and put a water hose in it until I couldn't see rust coming out. But like you said, you have to shake and twist and so that crap to get the big stuff out. I used a syphon pump to get the rest of the fluid/small stuff out. Good luck, took me about 2 weeks to restore the tank

Sent from my SNE-LX3 using Tapatalk
Seems like this is the only route. I had good luck with filling the tank with water and giving it a good shaking while it was inverted. Apparently there was so much rust sediment it had settled into little bricks the size of my thumb! I repeated this until the water ran clear and I couldn't hear any rattling inside. Using a trusty endoscope, I inspected the interior and can't identify any significant deposits. Pics to follow.

In go the drywall screws to scrape off what's left of the surface rust. If I stick a magnet pickup tool while shaking the tank around, I should be able to recover them.

You could use smaller things like 1/4" to 3/8" nuts.Or BBs.
On a day your wife is gone wrap a blanket around the tank and put it in the clothes dryer. ?
I'm living the bachelor life so I'll give the dryer a whirl if I'm feeling cheeky ?
 

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Discussion Starter #7
I managed to spend some time with the tank while sheltered in place. Even after two washes with MEK, there are still deposits of a failed POR-15 liner. While I wait for rubber stoppers and more MEK, here are some pictures from the interior:
285622

285623

The second image shows a more stubborn POR-15 deposit. I'll try a longer duration soak with MEK to lift it. With any luck, the liner will lift and flush out. From there, a vinegar or EvapoRust treatment should clear the rust for a Caswell epoxy treatment. Thanks for everyone who's helped out so far.
 

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It took long enough but I finally got her running. With the blessing of an air compressor and a generous dose of carb cleaner, I worked over the carburetors and got the engine humming. The tank was another story.

Method:

I plugged the petcock hole with an appropriately whittled-down wine cork and secured the cork with some painter's tape for good measure. I placed the tank inside a large plastic storage bin to contain any potential spills and propped the tank up on several blocks of 2x4 to keep the paint away from any drainage that might occur. Since I couldn't find more MEK, I filled the tank to the brim with acetone and let it sit for >24 hours. After draining most of the acetone back into its containers, I gave the tank a good shake and could hear a ton of loose debris.

With the petcock hole plugged, I filled the tank with water and shook it around while it was upside down to drain what flakes of POR-15 would willingingly leave through the fill hole. After repeating that cycle several times, I grabbed a flashlight and a pair of needle nose pliers. By creatively shaking the tank, I could get the larger POR-15 chunks and rust flakes to sit within view of the fill hole and pulled them out piece by piece with the pliers. This took quite a bit of patience since the debris would easily slide out of reach or refuse to settle within view without some major coaxing of the tank.

When I was confident the tank was as clear of major debris as I could manage, I put it back in the plastic container and added Evaporust. Since I could only find a gallon locally, I would shake the tank every few hours and rest the tank at different angles to soak all the internal surfaces over the course of ~36 hours. I drained the Evaporust and aggressively rinsed the inside of the tank with water. I added a pint or so of acetone to the tank and tried to displace the water as best I could before gingerly using a heat gun to evaporate what fluid remained without damaging the paint.

Content that the tank was dry, I wedged a telescoping magnet pickup tool into the front corners of the tank and shook the tank until the drywall screws I had put in earlier caught onto the magnet. Rinse and repeat until all the drywall screws were taken out.

I attached the petcock assembly and fit the tank back onto the bike before filling it with gasoline. For now, the bike runs like a top and the carbs haven't shown signs of refouling.

Discussion:

Since the tank's integrity wasn't compromised, I opted against resealing the interior. The gas should prevent most rust and I plan to ride the bike frequently enough that inevitable rust from the bare metal won't accumulate quickly enough to compromise the gasoline. I'll likely replace the bike before the tank has a chance to really rust over again.

I'm not knocking the performance of the POR-15 tank sealer and blame this failure on poor preparation. Though from what I've gathered online, proper application requires immaculate prep work and even that won't save you from an eventual failure of the sealant. Save it for when your tank has pinholes that can't be plugged otherwise.

Anyway, thanks for coming to my TED talk. I hope this write-up helps anyone who finds themselves in a similar position.
 
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