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1979 Honda CX500 Custom, 45,000.
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Discussion Starter · #1 ·
So I tried cleaning my tank my self with vinegar and bb's. I though it went okay at 1st, and then things got worse than before. This is my daily driver for now and I wanted it running right, it was cutting a little bit, so I changed the plugs, needed to fix the throttle cable, which I did, but when I took the tank off it sounded like there was a bunch of gravel in the tank (why I decided to clean it). Let it sit overnight with vinegar after shaking it up a bunch, flush it as best could, reinstalled it. Died on me about 2 miles down the road, clogged inline filter, flushed it again with fuel, replaced the filter and the same thing happened. So I said screw it and took it to a radiator place to have them wash it. Well, they called me today and said the tank has holes, wanted to show me before they continue. Once I go and look at it tomorrow, what are your suggestions on how I should proceed, I need the bike rolling as soon as possible. Never had to deal with rust issues on my other much newer bikes I have had in the past, not really sure where to start, and most shops I have called don't seem to want to touch anything but a Harley. Thanks in advance guys.
 

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I can not express how much I love the KBS tank seal kit, it worked perfectly removing the rust, cleaning and then sealing. It's a bit expensive for a sealer(around $70)but it's cheaper then a new tank.
 

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1979 Honda CX500 Custom, 45,000.
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Discussion Starter · #4 ·
Thank you, that is what I am probably going to end up doing, I will see what the tank looks like tomorrow. Hopefully I can just get him to send me some pictures in the morning so I can give him the go ahead with the acid wash or not. There are only a few on ebay right now, that I am watching of course but, I am thinking it is going to end up costing about the same as getting this one fixed and at least primer'ed up. I am moving this weekend and it is looking like I am going to need to find a truck to drag this thing to my new place, I was really hoping to be up and running by Saturday. If it is bad enough I am jut going to bite the bullet and with ebay and hope for the best. What kind of shop should I take it to if it needs more repair than I can do in the garage without a welder?
 

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1978 CX500 "The Grub", '83 GL650, '82 GL500 Project "AdventureWing", '79 CX500C, '78 CX500 Scrambler
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I can not express how much I love the KBS tank seal kit, it worked perfectly removing the rust, cleaning and then sealing. It's a bit expensive for a sealer(around $70)but it's cheaper then a new tank.
I hadn't heard of KBS. Thanks for the tip.
 

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81 Gl500i 83 CX650E
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I have had good luck with POR 15 , the Rad shop would be a good shop to have fix the holes , get them to remove the rust and then Silver solder the holes shut . Por 15 will seal pin holes but anything over a 1/16 inch should get a patch first. I use brass shim stock for small holes . Cheers
 
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'84 CX650E that is evolving into a GL500
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If it is already at the rad place ask how much it would cost for them to fix the holes and line it with epoxy. The last time I had one done they charged me less than the price of a kit to do it myself and that tank had holes I could have put my finger through.

The tank on my CX came from the GL500 I had previously (there are 2 long stories there). In 2003 I noticed that the 500's tank was wet along the bottom edge and when I drained it so that I could examine the bottom I noticed that the fuel coming out of it was distinctly red coloured. On the bottom I found a couple of blisters under the paint and one or 2 places where blisters had broken. When I sanded off the paint around the blisters I found more rust spots that were soft enough that I could pierce them easily. I tried to find a replacement but the local bike wrecker (who didn't have one in stock) told me to have it lined at a rad shop. They cleaned the tank, soldered up the holes that were open and lined it for me (this one cost about the same as the kit to do it myself too). They worked with the hazardous chemicals and dealt with any mess and the leaks have not returned 18 years later.

Note that if there are holes you will have to re-paint the tank, at least in the area where the holes are.
 

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1979 Honda CX500 Custom, 45,000.
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Discussion Starter · #9 ·
Thank you for the reply guys, I just talked to the guy at the rad shop and he is not even willing to proceed with the wash. Something about him doing it for a buddy and the dudes bike caught fire after the repair and burned his nuts, ouch. So I have to go pick it up and see what I can do myself, or find another tank as soon as I can. I am thinking about ebay, really don't want to $300 on another tank that may have problems like mine, mine looked fairly clean from up top too, until i shook it around lol.
 

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If there are no other rad shops near you perhaps you should try repairing it yourself. You've got nothing to lose by trying and may gain some new skills necessary to keep old bike running.
 

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'84 CX650E that is evolving into a GL500
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If it caught fire he obviously didn't seal it properly. If there are any other local rad shops you could call around and see if any of them can repair it for you.

As for finding a replacement from a reputable source, ask in the Selling & Buying section of the forum. Just be advised that we've had a problem lately with scammers signing up and replying to parts wanted posts with contact information for a "friend" who purportedly has exactly the part needed in order to try to part people from their money. Reputable sellers will have at least a few posts on the forum that you can find by mousing over their avatar (anyone reported to have scammed a fellow forum member will be investigated and if guilty will be banned) and are usually willing to send you pictures of the actual item that they have
 

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Thank you for the reply guys, I just talked to the guy at the rad shop and he is not even willing to proceed with the wash. Something about him doing it for a buddy and the dudes bike caught fire after the repair and burned his nuts, ouch. So I have to go pick it up and see what I can do myself, or find another tank as soon as I can. I am thinking about ebay, really don't want to $300 on another tank that may have problems like mine, mine looked fairly clean from up top too, until i shook it around lol.
The KBS tank repair can fill pin holes, and its really just a fuel safe epoxy that if you fallow the instrustion will completely cover every inch of the tank with a super durable layer, I used some of the under body coating for a 73 Volkswagen restoration a few years ago and hitting it with a mini sledge hammer did almost nothing to the coating (bent the metal of course).
But as long as your holes are not to big it should seal it up just fine, and the "klean" part of the kit is a type of acid that eats the rust and then leaves a layer of zinc to prevent flash rust.
 

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I hadn't heard of KBS. Thanks for the tip.
No problem, They are one of the secret little gems I found working on a Volkswagen a few years ago. They use to be a small mom a pop shop, that makes some seriously good products and a genuinely a good company that actually is helpful if you have questions. It has always been awesome to work with there products so I feel like I should tell people about it when the opportunity come up.
 

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1979 Honda CX500 Custom, 45,000.
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Discussion Starter · #14 ·
I am going to pickup the tank after work, there is a bike boneyard near there I am going to check out and go from there. There are plenty of radiator shops around, just have to find one willing to do it.
 

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I bought a Honda cb750 a few years ago that sat since the early 80s. Entire tank was varnished and full of black sludge. Was told the tank was rusted through. After multiple attempts with multiple different rust removing products and techniques. The only thing that worked for me to remove the rust was muriatic acid. And it worked in minutes. Lots of research and proper precautions and prep on your end would be recommended before going that route but afterwards the tank looked brand new inside and held gas just fine.
 

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You might try joining the facebook group "Honda CX 500 e 650 Turbo " many people from all over the world, you could put out a request for a gas tank and you might get a hit at a reasonable price.
 

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1978 CX500, 1982 GL500 Silverwing Interstate, 1980 CX500 Custom
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Great tip on the KBS Sealer. I've been experimenting over winter with various sealers on a GL500 tank, and will try this next.

One thing I would like to suggest (and this worked for me on a British Gas tank) is to apply an electrolysis technique. Rather than removing the rust, which can expose more holes, electrolysis will convert the rust back iron. It's not pretty (kind of black) but if you coat after that it should seal pretty well.

I built a kit to do this using a battery charger (newer ones will also require a battery as a "load"), and a few small parts from a hardware store (a tub, the washing soda). If you have some cables and a sacrificial iron rod/nail your outlay is pretty low. There's loads on YouTube about it (see below for examples and a web page too).





Cheers, and good luck, Adrian
 
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Discussion Starter · #20 ·
Thanks for the replies guys. I checked Bobs, they did not have a tank that was any better than mine. I ended up buying a rather expensive one off of ebay, not dents or visible rust, but of course it got dented somewhere during delivery. I got $80 back though from the seller, they did not bubble wrap it, popped the dent out with a air wedge. Took it out for a spin last night and had a nice camera take a picture of me. Went to go run an errand this morning and I am leaking gas out of one of the carb vent tubes, my bad luck is limitless if anyone needs some, free shipping. Anyway, looks like a carb rebuild is in my very near future. Stuck float?
 
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