ST1300 - Rust in Petrol Tank

HelloEveryone

Joined
Oct 20, 2025
Messages
91
Age
57
Location
Singapore
Bike
ST1300
Changing a new fuel pump assembly that comes with petrol filter etc and saw the condition of the rusted sub tank.

Negligent from previous owner either allowing slight rain water seepage into petrol tank from tank cap or not filling up the petrol tank in storage and over the years, this is what happens.

Decided to order a new sub petrol tank and main tank and time to service all injectors, new fuel line and time to service throttle body etc
 

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Personally. I'd also change the Lower Tank (it's constantly fed fuel by the upper tank via the elbow hose (in first pic)

I'd remove the upper tank Float level (4 nuts) to verify it has any rust in it?
before ordering/painting a replacement tank. (highly unlikely? surely possible?)

Did the bike run before you tore it down?
 
Rockstar said:
Personally. I'd also change the Lower Tank (it's constantly fed fuel by the upper tank via the elbow hose (in first pic)

I'd remove the upper tank Float level (4 nuts) to verify it has any rust in it?
before ordering/painting a replacement tank. (highly unlikely? surely possible?)

Did the bike run before you tore it down?
Click to expand...

Managed to got a new Main Tank (White) with original Honda emblems and a new sub tank.

Yes surprisingly with all the rust, it runs pretty well. That’s Honda built quality even under these conditions

I think the fuel pump filter did a good job in the petrol filtration.

Luckily I decided to change the fuel pump assembly to have noticed these.
 
I have "cleaned" tanks by putting clean gravel into them and rolling them, I am cheap that way and some tanks can get to be a bitch to find.
Wish I could get my hands on your old ones. They would be fun to airbrush.
 
motornut said:
I have "cleaned" tanks by putting clean gravel into them and rolling them, I am cheap that way and some tanks can get to be a bitch to find.
Wish I could get my hands on your old ones. They would be fun to airbrush.
Click to expand...
Too far away and items too large the shipping cost may not be worth jt
 
New Sub-tank and fuel pump assembly finally in with new fuel lines etc

O-rings for the fuel injectors and FPS fuel pressure sensor

Throttle body spanking clean too now
 

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I just repaired the same problem using POR 15. The lower tank was a complete mess. To reduce the amount of POR 15 I needed, I filled the lower tank with golf balls. Used two 1 Quart jugs diluted 50% with water. Completely filled lower tank with solution and let sit for 24 hours. The results were impressive. Then replaced fuel pump and filters with Kit from Quantum. Performance has been restored and no more intermitend fuel starvation issues. One cautionary note. The metal seal on the top of lower tank is easily bent and can cause leaks when reintalling the Pump and filter tree. Use caution not to bend that seal flange.
 
BTDT!

I had "cleaned" my 04's lower tank, only to have it re-rust on me. So I replaced it and the fuel pump. It's been running good for the last three years now. And when I know it will be sitting, I've been putting non ethanol gas in it and my 2012.
 
SupraSabre said:
BTDT!
I had "cleaned" my 04's lower tank, only to have it re-rust on me.
Click to expand...
Bob, Did you use POR or a similar product?

I've used POR and found it's cleaning stage doe a pretty good job of etching the steel down to bare metal, (just like Ophospho treatment). The second stage uses a vile smelling coating that seals the metal. Having been there w/ POR, I'd guess that prep, as usual, is mostly all, because the coating process is also vital. If you miss a spot, the coating will not protect the metal well and might not stick.
 
SMSW said:
Bob, Did you use POR or a similar product?

I've used POR and found it's cleaning stage doe a pretty good job of etching the steel down to bare metal, (just like Ophospho treatment). The second stage uses a vile smelling coating that seals the metal. Having been there w/ POR, I'd guess that prep, as usual, is mostly all, because the coating process is also vital. If you miss a spot, the coating will not protect the metal well and might not stick.
Click to expand...

No, I used a rust remover, but I let the bike sit again for quite awhile. When I got back to it, I replaced the lower tank and the fuel pump.

That's in my 2004 :bl13:, and I've kept it on the road since. :)
 
Evaporust works very well at removing rust. It does require that any loose rust be removed first, so if its really bad you'll need to find a way to do that.

Vinegar also works very well at removing rust. Unless the tanks had holes or were REALLY bad, just cleaning the rust makes more sense.
 
2008 ST1300 stalling after long storage, rusty tank and fuel pump questions

Hi everyone,

I have a low-km 2008 ST1300 that sat in the shed for a long time. It was running well when I bought it, but after about 100 km it started to stall.

The main tank was very rusty up to the neck, and it looks like someone had tried to clean the rust before. The previous owner also told me they cleaned the fuel pump with some kind of ultrasonic cleaner. The tank cap isn't original either, so I think it needs replacing.

I cleaned the main tank with Evapo-Rust, then with vinegar, which left flash rust, so I did the Evapo-Rust process again. I can't see all the way inside, but I believe the rust is gone. I found a couple of pinholes and treated them with welding putty. I then filled the tank with fuel to test and there are no leaks so far. The lower tank has a light, powdery coating on the inside.

I'm not very experienced with this kind of work and I'm trying to save some money, but I'm still open to paying for professional help if that's what it takes.

My questions:
  1. Do you think this is too much of an amateur job? Am I likely to end up redoing everything?
  2. Do I need to replace the whole fuel pump, or is a new filter and gasket enough? I plan to use POR-15 on both tanks afterwards.
  3. Before sealing the main tank, how do I block off the fuel lines and outlets so the sealer doesn't clog them or change their internal size?
Thanks in advance for any advice!
 

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Ben F Bengu said:
2008 ST1300 stalling after long storage, rusty tank and fuel pump questions

Hi everyone,

I have a low-km 2008 ST1300 that sat in the shed for a long time. It was running well when I bought it, but after about 100 km it started to stall.

The main tank was very rusty up to the neck, and it looks like someone had tried to clean the rust before. The previous owner also told me they cleaned the fuel pump with some kind of ultrasonic cleaner. The tank cap isn't original either, so I think it needs replacing.

I cleaned the main tank with Evapo-Rust, then with vinegar, which left flash rust, so I did the Evapo-Rust process again. I can't see all the way inside, but I believe the rust is gone. I found a couple of pinholes and treated them with welding putty. I then filled the tank with fuel to test and there are no leaks so far. The lower tank has a light, powdery coating on the inside.

I'm not very experienced with this kind of work and I'm trying to save some money, but I'm still open to paying for professional help if that's what it takes.

My questions:
  1. Do you think this is too much of an amateur job? Am I likely to end up redoing everything?
  2. Do I need to replace the whole fuel pump, or is a new filter and gasket enough? I plan to use POR-15 on both tanks afterwards.
  3. Before sealing the main tank, how do I block off the fuel lines and outlets so the sealer doesn't clog them or change their internal size?
Thanks in advance for any advice!
Click to expand...

Given the age of the ST13, this would become a common issue unless tank during storage it kept full etc

I guess the first thing is to find out where the rust is coming from and normally that would be water entering the tank and to the sub tank.

The main culprit would be the top tank refill cap where there is a drainage hole when petrol is overfilled it will escape through this.

If it is blocked, rain or hose water may be trapped and the tank cap rubber submerged below it may not fully block the water from entering the tank causing initial rust to be form at the lip of the refill tank inlet.

I didn’t get around cleaning the inner tanks but there a shop that can actually clean the tank and recoat the inner tanks too.

My mechanics suggested I replace it given the severity of the rust inside the tank.

And yes mine was caused by that petrol drainage hole at the top that was plugged and water was just hovering around the cap areas after every wash or rain.

I believe the petrol can get contaminated with the rust, however the fuel filter will do an excellent job in filtration unless the fuel filter itself is clogged. The fuel filter is a replaceable part on the Honda parts list.
 
Haven't been on here in a long time, been looking at an ST1300, they are all getting old and high mileage mostly now like ourselves!
reading this thread has made me think, do I really want to start sorting out headaches like this on an old high mileage bike?
still love the V4 pans though, unfortuneately the carbed ST1100 isn't an option here because the only choice in petrol/gas we have in Ireland is that horrible E10 crap.
I have no real need for an St1300 other than I love how they ride and also the look of them. Think it would be a Winter and wet weather bike which is most of the year here!
 
broc11 said:
Haven't been on here in a long time, been looking at an ST1300, they are all getting old and high mileage mostly now like ourselves!
reading this thread has made me think, do I really want to start sorting out headaches like this on an old high mileage bike?
still love the V4 pans though, unfortuneately the carbed ST1100 isn't an option here because the only choice in petrol/gas we have in Ireland is that horrible E10 crap.
I have no real need for an St1300 other than I love how they ride and also the look of them. Think it would be a Winter and wet weather bike which is most of the year here!
Click to expand...
Treat it as a hobby or past time restoring and maintaining a Legendary Tourer if time permits.
 
There is a plating on the inside of factory tanks. Once the rust starts if not sealed it will eventually rust again. POR15 works great, follow instructions carefully.
 
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