Is this tank rust? -- And, what's with my petcock? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 11-08-2009, 05:25 PM Thread Starter
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Is this tank rust? -- And, what's with my petcock?

For a while now, my 1994 VN750 has had a problem maintaining idle after about 10 minutes of riding. Up until then, things are normal; then gradually, it's harder and harder to idle, until I have to rev to 3K or more to keep it from sputtering out at stop lights and stop signs. This is a problem, as to slow down for stopping I'd like to use my front brake, which is hard to do while also keeping my revs up by throttling. But if I park the bike for a while it's normal again the next time I start riding, but only for 10 minutes.

I tried seafoam, no good. I checked my airbox and battery, both are clean and working fine. The bike does not shudder or accelerate jerkily as would happen with dirty carbs (which I've experienced). So then, what?

Based on the symptoms people on this board and others have suggested it was likely to be a fuel intake problem based on something in the tank eventually clogging the petcock. Today I finally got around to taking the tank off and emptying the gas into a brand new plastic tub (with a drain spout) and it looked like this:




At first I thought that red/orange debris was leaves that had fallen into the tub from the trees overhead. Then I realized they're probably rust chips. Darn!

I poured the gas into a canister through a filter to catch this stuff, intending to refill my bike with this. But after removing my petcock and reinstalling it, it leaks fuel from somewhere. Darn #2!

The reason for this may be that I disassembled my petcock more than necessary. I was looking for a filter on my petcock like the diagram in the Clymers book shows it, and the BikeBandit parts schematic for the shutoff valve assembly -- something that looks like the fin on a submarine. But when I pulled my petcock out of the tank, it just had the two fuel lines, one long and one short (for the reserve setting). When I didn't find one, I continued disassembling the petcock and remove the diaphragm as well, perhaps tearing some kind of seal that is no longer tight. Rats!

So... now what? I can get a new petcock if necessary, but what do I do about the apparent rust in the tank?

P.S.: Is there an easier way to "drain the tank" than holding it upside down and pouring the gas into a tub out of the point of entry? It was kind of messy, and gasoline is not something I want to be messy with.

"Until you have the courage to lose sight of the shore, you will not know the terror of being forever lost at sea." (Despair.com)

Last edited by robardin; 11-08-2009 at 05:50 PM.
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post #2 of 10 (permalink) Old 11-08-2009, 05:38 PM
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I believe there are a few threads on cleaning rust out of your tank , which is the first thing to do.

Many then use a tank sealant like POR ir KREAM to coat the tank and seal out future issues with rust.

I would suggest getting a new petcock, complete with the filters that yours seem to no longer have.

It does now sound like your carb problems were a direct result of crap in your fuel tank.

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post #3 of 10 (permalink) Old 11-08-2009, 08:23 PM Thread Starter
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How can I tell if it's rust or "carmelized" gas of some kind? I'll be honest, I don't really know what that means, except maybe that the tank was left full and without stabilizer for some long period and the gasoline evaporated away, leaving residual stuff that built up over time.

It seems odd if that was the case for me, as I've ridden it pretty regularly for the time I've had it. True, that's only been about 1-1/2 years on a bike from 1994, and before that, I really have no idea how it was treated; but a rusty tank should have hit me before 3 weeks ago then, no?

I looked inside the tank with a penlight and it doesn't look rusty. I'd prefer to just swap in a new petcock, which I have to do anyway since it looks like I've ripped the diaphragm at a minimum -- oh, that sounds naughty -- and and it surprisingly doesn't have a filter cover on the two fuel sippers, and see what happens. I mean, if I have that filter and the tank is rusty, I won't be doing any additional or irreversible damage that way, would I?

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post #4 of 10 (permalink) Old 11-08-2009, 09:09 PM
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Quote:
Originally Posted by robardin View Post
How can I tell if it's rust or "carmelized" gas of some kind? I'll be honest, I don't really know what that means, except maybe that the tank was left full and without stabilizer for some long period and the gasoline evaporated away, leaving residual stuff that built up over time.

It seems odd if that was the case for me, as I've ridden it pretty regularly for the time I've had it. True, that's only been about 1-1/2 years on a bike from 1994, and before that, I really have no idea how it was treated; but a rusty tank should have hit me before 3 weeks ago then, no?

I looked inside the tank with a penlight and it doesn't look rusty. I'd prefer to just swap in a new petcock, which I have to do anyway since it looks like I've ripped the diaphragm at a minimum -- oh, that sounds naughty -- and and it surprisingly doesn't have a filter cover on the two fuel sippers, and see what happens. I mean, if I have that filter and the tank is rusty, I won't be doing any additional or irreversible damage that way, would I?
If it's rust, it will be attracted to a magnet. Doubt it is carmelization, as I would think the Seafoam would have dissolved it. If you have a dentist's or mechanic's mirror, get it and some light inside the tank. Should be able to see the rust. More than likely, any rust is going to be in the lower (the part nearest the rider) portion of the tank. Unless you have pinholes in the tank, I don't recommend lining it. I recently went through the process of removing an improperly installed liner in one of my tanks. Rust was everywhere under it. Once I got the rust out, keeping the tank full (reduces condensation) and periodically using Seafoam to remove moisture in the tank should keep any rust from forming.

Your petcock options appear to be: 1. rebuild the innards of the one you have (filter screens are not available as parts) and put filters in the fuel lines below the petcock, 2. buy a new one (expensive) that will have the screens on it, or 3. have someone fabricate custom filter screens for your existing petcock (probably also expensive).

Good luck!

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1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
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post #5 of 10 (permalink) Old 11-08-2009, 10:37 PM Thread Starter
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Originally Posted by flitecontrol View Post
If it's rust, it will be attracted to a magnet.

...Unless you have pinholes in the tank, I don't recommend lining it.

...Your petcock options appear to be: 1. rebuild the innards of the one you have (filter screens are not available as parts) and put filters in the fuel lines below the petcock, 2. buy a new one (expensive) that will have the screens on it, or 3. have someone fabricate custom filter screens for your existing petcock (probably also expensive).
Good point about the rust = metal = magnetic attraction. I just went and did that test with a refrigerator magnet and sad to say, it definitely is rust.

What do you mean by "lining it"? Is that what that KREEM stuff amounts to? That stuff ain't all that cheap either, about $40 for the three necessary components from Motorcycle Superstore, plus some horror stories about using it.

There's some kind of drawn out, salt-and-vinegar plus electricity electroplating method, and another with acid, hmmm.... Decisions, decisions. I like this description about using acid last referred to by fergy, particularly the part about taking just 3 hours -- good for the "shiftless and lazy"

As for the petcock, I did find aftermarket rebuild kits that cost about $40, and getting an OEM petcock was $60, so I just went and got a replacement stock petcock. I'm not sure what I did to get mine to leak, whether it's the diaphragm or the O-ring, and in any case would like to have a normal filter there, and I'd rather not try one thing and then another and end up taking a month to fix this over just to try to save $30 or something that I may end up spending anyway.

"Until you have the courage to lose sight of the shore, you will not know the terror of being forever lost at sea." (Despair.com)
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post #6 of 10 (permalink) Old 11-09-2009, 01:21 AM
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Quote:
Originally Posted by robardin View Post
Good point about the rust = metal = magnetic attraction. I just went and did that test with a refrigerator magnet and sad to say, it definitely is rust.

What do you mean by "lining it"? Is that what that KREEM stuff amounts to? That stuff ain't all that cheap either, about $40 for the three necessary components from Motorcycle Superstore, plus some horror stories about using it.

There's some kind of drawn out, salt-and-vinegar plus electricity electroplating method, and another with acid, hmmm.... Decisions, decisions. I like this description about using acid last referred to by fergy, particularly the part about taking just 3 hours -- good for the "shiftless and lazy"

As for the petcock, I did find aftermarket rebuild kits that cost about $40, and getting an OEM petcock was $60, so I just went and got a replacement stock petcock. I'm not sure what I did to get mine to leak, whether it's the diaphragm or the O-ring, and in any case would like to have a normal filter there, and I'd rather not try one thing and then another and end up taking a month to fix this over just to try to save $30 or something that I may end up spending anyway.
dont use kream Dont use kream... with your tank empty it will only take moments for the rust to start forming inside ...
for rust removal and protection do this rust removal click here

this removal works great ... and will be done by the time your petcock arives



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post #7 of 10 (permalink) Old 11-09-2009, 08:34 AM Thread Starter
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Originally Posted by seebeeare View Post
dont use kream Dont use kream... with your tank empty it will only take moments for the rust to start forming inside ...
for rust removal and protection do this rust removal click here

this removal works great ... and will be done by the time your petcock arives
True that, and somewhat less dangerous. I can set it up and let it mostly run on its own, I hope; the directions say to check "every few hours", which I hope can be "every 12 hours" because I won't be home most of the day.

"Until you have the courage to lose sight of the shore, you will not know the terror of being forever lost at sea." (Despair.com)
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post #8 of 10 (permalink) Old 11-09-2009, 09:18 AM
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Definitely don't use a sealer in the tank like kreem! I can refer you to several horror stories on this forum and the yahoo group about the results of that stuff. Also, not trying to change your mind about the acid method, but it is not dangerous as it might sound. It can be messy if you don't prepare for it. Wear old clothes and eye protection, rubber gloves etc. Have your garden hose right there ready to rinse any spillage. It is quick and very effective, and the navel jelly treatment after the tank is clean of rust treats the metal so new rust won't form. It's also cheap and definitely the quickest method.
The muriatic acid is something that probably every pool owner uses on a regular basis, pouring into the pool water for lowering the PH I believe, so it isn't like you are playing with nitro! Do be careful and don't breathe in the vapors, but you won't blow yourself up or something like that! Just my .02!

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post #9 of 10 (permalink) Old 11-09-2009, 09:22 AM
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I wanted to go the electrolysis method, since it adds metal to the tank rather than removing it. But my battery charger was "smart" and wouldn't charge the wires because it could sense there wasn't a good connection. I wound up doing the acid procedure.

The minimum amount of muriatic acid I could buy was a gallon at $6. Found a post where the guy used "The Works" toilet bowl cleaner ($1.12 for a quart at Walmart). It's 30% hydrochloric acid and one container treated two tanks with lots left over. Rust disappears on contact with that stuff!

Yes, when I mentioned tank liner, I was referring to Kreem and other tank lining materials.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
_____________________________________________
"Black Beauty"
1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

Old Blue
2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts

Last edited by flitecontrol; 11-09-2009 at 09:25 AM.
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post #10 of 10 (permalink) Old 11-09-2009, 09:32 AM Thread Starter
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Quote:
Originally Posted by seebeeare View Post
for rust removal and protection do this rust removal click here

this removal works great ... and will be done by the time your petcock arives
Hm, looks like I'll have to upgrade from my Battery Tender Jr., it's only rated at 750 mA and the directions require at least a 6 Amp one, and uses a 10 Amp charger as an example.

Right now Sears has a sale on chargers, a DieHard 10 Amp manual battery charger for $35, or a DieHard 10/2/50 Amp charger with optional maintenance free mode for $45 (meaning, I could set it to "non-smart" so it wouldn't shut off the way flitecontrol described). Sounds like I should go for the second one so I could safely use it on my bike.

"Until you have the courage to lose sight of the shore, you will not know the terror of being forever lost at sea." (Despair.com)
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