Hello All:

Checking Youtube for videos on gas tank derusting, I came across this video on the KBS Tank Cleaner and Coating System:

https://www.youtube.com/watch?v=Sf2veir5VHU

There are several more also, but this one is by the maker KBS.  This kit comes with a cleaner, a rust remover, and a coating compound to supposedly put a rust and fuel proof coating on the inside of the tank.  It looks like 2-3 hours of work to do all the steps (it takes an hour of holding and rotating the tank to get the compound evenly all over the inside).  They claim this is a permanent solution to tank rust. 

The kit is available at the below Amazon link for $42. It gets 4 out of 5 stars on almost 200 reviews, with 63% of the reviews being 5 stars.   

https://www.amazon.com/KBS-Coatings-52000-Sealer-Gallon/dp/B000IBDIX2/ref=sr_1_1?dchild=1&keywords=KBS+Cycle+Tank+Sealer+Kit&qid=1588787081&sr=8-1

If any of you have used this on your bike, I'd appreciate hearing about the experience and how it worked for you. 

If this works as advertised, I'm liking the idea of combining this with an On/Off fuel valve in the line to the carbs to allow sucking the carbs dry to provide a permanent solution to the carb fouling problem. 

Fudge, double fudge and hell no.

The first chemical is muriatic acid. Available for $3 or under a gallon.
Second chemical is Acetone - Methyl ethyl ketone is better. And also $5 or so a gallon - careful, this frucker eats paint.

The coating - well be very careful and make sure you don't get too thick, or it will peel off.

OK remove rust - muriatic acid.
Now here it gets a little tricky - because I have not had proof - is only held on 8 or so years after I modded the tank to 0 drain (fitting a vent tube on top). a very dilute - like 1/10 quart in 1 gal of hot water of the por 15 prep stuff. The reason why I recommend this is - it coats the tank with some type of chemical prep crap to get the POR 15 coating to glue itself up onto it. The problem is - the 0 drain - GS tank holds too much liquid unless you modded it for 0 drain, and the one I didn't mod that way failed miserably.
So prep it with that POR15 prep stuff.
Then again 0 drain works best, but otherwise, put 1/2 pint of the por 15 and slosh it about. The nput some tupe of dog chain in the tank, slosh for 1-2 hrs and get that chain out with all the excess crap POR15. A thin layer of it adheres well to the prepped metal. Thick layer, comes off like its a creature.

My recommendation is muriatic acid, then the dilute version of their prep and then POR15 as light as you can get with all the excess removed.

Cool.
Buddha.

Basically I'm saying understand the chemical processes behind these products. And some physical properties too.

Steps - explained by chemistry.
1. Removal of rust - always best accomplished by muriatic acid. I prefer to use this for the shortest time possible so I use a little of it at full strength. Then repeat if needed.
2. Neutralizing the acid - baking soda works, but dilute the acid out with water first. The longer it stays wet, the easier for the rusting to re occur. I prefer to rinse with hot hot hot water. And only use tiny bit of baking soda at the last rinse.
3.Pepping surface for the paint - again this is an acid - sort of. You want to prime it with the "prep" chemical - again dilute it and let it sit a while. Potassium metabisulphite (if I recall is the adhesion promoter they use in POR15 - likely same in all others).
4. Get all of it out and as dry as you can get - this is where a GS tank fails miserably. You can never get it dry, I installed a vent in the top of one tank, tuned out to be my best coat job - ever.
5. Coat it with the stuff, and make sure the excess is all removed avter its been put on every spot of the tank in even thickness - yea good luck without a 0 drain vent, or maybe maybe maybe a chain that allows you to both scrape the tank, coat the tank and get the excess out - and hopefully not get it on the paint.
6. Let it dry and cure and harden. - Here a hot car parked in the sun with windows up works well.
7. Put it on and ride. Yea coated tank feels great.

Fingers crossed, and hope in 10 yrs it doesn't come loose.

Cool.
Buddha.

Eugh... chemical tank liners. People use them when the tank isn't even leaking? Why on earth? there's the possibility that the chemicals can over time, leach into your fuel. (Clogged jets anyone?) And when (not if) it needs to be stripped out it'll be a nightmare job.

Jools - the liners will not ever get in and clog the jets.
If you don't do it right, the tank will rust under the liner.
You would have to de-rust and clean it anyway. The liners are put in after that.

If not done right, and the liner comes loose, and you have rust under it, then you need to cut the tank, get your hand in and get the liner out. Its problem is adhesion and protection, not exactly dissolving and clogging.

Cool.
Buddha.

Buddha, thanks very much for the detailed comments.  It sounds like you are generally in favor of this idea, and just think that KBS kit is overpriced. 

Jools, the idea here is to try to figure out a reasonable set of actions that reduces the fouling of the carbs to near zero.  I might define that as an initial investment of 6-12 hours to set the bike up (tank derusting/treating, add extra valve to allow running the carb dry if it not to be used awhile), and then no more than 4-8 hours a year of effort (treating the fuel, draining carb dry, winterizing the tank) to keep the carbs from fouling for a period of many years.   

It seems there are three common liners.  They are rated on Amazon as follows:

KBS:  63% 5-star, 10% 1-star.
POR-15: 76% 5-star, 6% 1-star.
Kreem: 72% 5-star, 6% 1-star.

The 5% to 10% 1-star reviews are mostly failings of the liner.  For each of those, there seem to be 5-8 people who say it works perfectly or nearly so. 

The other two options to self-treating and lining the tank seem to be:

1.  Use a fuel filter and derust the tank yourself every year or two.  If you are taking the tank off annually to winterize, that would seem to be only an hour or two of extra effort.

2.  Going out to a professional company that has perfected rust removal and linings via a repeatable professional process.  For example, at http://gastanklining.com/ they guarantee their work and charge $349.  The price is a stinger, but it is about the same as one professional carb cleaning.  I've gotten so allergic to this problem I am considering that investment.  Pay $349 once, never have to worry about the tank again. 

Guarantee for how long is the question. I have had the worst tanks I did still run over 7-8 years

Seriously, I have a tank I did 10+ yrs ago holding up. On a GS tank, you can not make it 10+ without making it 0 drain. You will need to get the tank wet and dry at a rate that is too rapid unless if was 0 drain.
Then it doesn't even matter what you use, but that tank running 10+ yrs was coated first with por15 and powdercoated outside after - POR15 will take the heat of powdercoating, kreem will not - ask me how I know.

Kreem can be removed to an effective degree if you had a failure with acetone, paint stripper etc, and in a way it actually re seals with acetone especially. POR15 has to be cut and scraped out.

Good concept, very very hard to execute in a tank that keeps 1/2 quart volume and you cant get your hand in a scrape it and what not.

Hey, maybe get a bottle brush with metal bristles - if one doesn't exist we should make it. The stem should bend and flex, but the bristles would stay stiff and scrape. That would let you get stuff nice and deep in the walls and get the excess out.
Otherwise, a dog chain, and a magnet on a extension shaft seems the best bet to get it out.

The problem is to get these things into the metal, as well as get that metal prepped to accept these with best adhesion. 0 drain helps with all of those. But if you manage to get the paint on to a well prepped surface and get just the right amount and not a gopping excess, it does stay on forever. BTW I got a few splotches of the pain on my driveway. The longest lasting, most impossible to get off is where I got a lot, and immediately scraped it off with my hand. That's about how thick por15 needs to be on there for it to stay on forever. And it needs to be on a surface about as rough as a concrete driveway.

The KBS crap is red. As in, the color of rust. So you cant tell if its getting rusty or not. No thanks. Kreem is white, and put the correct amount in ,and its like a lacy film. Good. POR15 is steel grey. Correct thickness, is hard to judge from color. But atleast its better than rust red.

Cool.
Buddha.

Buddha, thanks for taking the time to provide such a detailed reply.  I have to display my ignorance and ask...What is an "O drain" and what does it do? 

The tank in my 2001 is not bad.  It seems to have only a fine, thin layer of corrosion.  It may be that a muratic acid wash every other year would keep it clean enough.   

I have talked in detail with the owners of two professional high volume tank restoration operations.  They seem to offer an outstanding permanent solution for about $500 to $550 total, if you are willing to put that into an old GS500.  Maybe some of us are, since it seems buying an old rusty tank is still $200 to $400.   

One was Tony of GTL (http://gastanklining.com/), located in California.  He reports these key points.
1. He guarantees the product for as long as you own the bike, but the warranty is not transferable if you sell.  He will repair or replace the lining if there is any problem.
2.  The material is a phenol novolac 2 part epoxy (see https://www.corrosionpedia.com/definition/6532/epoxy-phenol-novolac-epn).  A similar process is used by Harley and BMW in their new bikes, but he reports he uses much more of the stuff and thinks his will last much longer than theirs do.  Harley/BMW warranty their tanks for 7 years.  It takes Harley/BMW a few minutes and a few dollars of material to treat a pristine new tank, but says there is about 4-5 hours of labor involved for them to do the whole process on rusted tanks.
3. They have been doing it a little over 10 years in a 2-3 man operation, and have treated nearly 6000 tanks.  About 0.5% of the tanks have come back for repair under the warranty, so that is about 30 tanks out of 6000.  If those are concentrated in tanks over 5 years old, that would imply about 0.1% failure rate per year after 5 years.   
4.  Shipping cost both ways runs about $130 for about 1000 miles, but there is no tax.  So, total cost about $350 + $130 = $480. 
5.  Turn-around time is currently about 1 month. 
6.  The Japanese manufacturers are not doing this, but are using a corrosion inhibitor process with something like a zinc chromate coating.  It works pretty well, much better than bare steel, but is not nearly as long lasting as these epoxy liners.  He reports he starts getting Japanese tanks in for his process as new as 2-3 years old. 
7.  For 20 years before starting this business, Tony was in the bike painting business.  But, the demand for this was so strong that he decided to start a business doing just tank derusting and lining.  It has been a good business for him for 10 years now.  They have actually stayed busy through the Covid lockdown as bike owners think this is a good time to get the tank off their bike and fix a long festering problem. 

The other was George of http://www.motorcyclefueltankservices.com/, which is in Florida.  Key points as follows:

1. They seem to be the highest volume operation in the business.  They have 19 employees and average 80 tanks per day.
2. They also have a lifetime warranty.  They have done over 700,000 tanks since 1977, and report effectively zero failure rate. George says he cannot remember the last time he had to fix one of his tanks. 
3. They start with an electrochemical rust removal process, then a galvanic process to lay down a corrosion inhibitor.  A vulcanization process to deposit the liner is the last step.  George does not disclose the coating, but they call it "porcelainization". 
4. The normal price for a tank that has no existing liner to remove and is not extensively rusted (no pin holes) is about $500 to $575.  But, George will offer a discount to members of this forum for a decent condition tank of $375 (just ask for George and say you would like the GStwins discount).  Depending on where you live in the United States, the two way shipping will cost you about $100 to $200.  I forgot to ask George about international shipping rates.   

0 drain is where you can drain the tank dry.
GS tank inherently is about 1/2 quart away.
Several tanks I know are 0 drain - Kz440, honda nighthawk etc. If you can tip the tank into various positions and get it dry in a few mins, its a 0 drain tank.
I installed a welded drain tube on top to make one tank t a 0 drain.

Yea that warranty I'd collect on it for atleast 1 tank by now. But atleast I am not out $375.

The GS tank isn't likely to last over 5-6 yrs unless you make it a 0 drain - or are very very lucky. He's counting on the fact a GS in 4-5 yrs will be either tossed in the trash, or sold, or ctually, all bikes get sold in 4-6 yrs anyway.

Cool.
Buddha.

Quote from: The Buddha on May 07, 2020, 03:13:44 PM

The GS tank isn't likely to last over 5-6 yrs unless you make it a 0 drain - or are very very lucky. He's counting on the fact a GS in 4-5 yrs will be either tossed in the trash, or sold, or ctually, all bikes get sold in 4-6 yrs anyway.

WHat? I've had my GS500 for 12 years. I've never done anything to the tank except run gasoline through it.

If MaxD also expects to own the GS for the long haul, I think $400 is money well spent to have a reliable gas tank (assuming the tank is solid and has good OEM paint and graphics and no dents). I would pay that rather than have to derust the tank and/or open the carbs up every couple of years.

You will never get that $400 back if you go to sell the bike. I say only do it if this is your motorcycle for the foreseeable future.

I'm just utterly flabbergasted by the amount of dosh being discussed here - seems to me it'd be much more pragmatic to either pay someone to ride the bike regularly, or just sell the bike and hire one for the occasions you absolutely MUST ride for whatever reason.
Biking is a lifestyle; the nurture, the maintenance, the pain & the pleasure, it's all part of the THING that biking is about. Seriously feel that OP would be much happier if he just hired when he feels the need - a lot less hassle & a lot more aligned to his lifestyle, probably cheaper too...
Sorry if that upsets anyone, but just my 2p's worth...

Buddha, that's great info, thanks. 

Blue, if it were not for having this group available for the expert advice, I probably either would do without having a motorcycle, or switch to a CB500X.  But, with all the outstanding help, it becomes much easier to take care of the bike, so I expect I will keep it.  My first bike was a 1979 Honda CX500 I bought new (except for my $100 90cc Honda Passport, I've never owned anything but 500's).  It was a little V-twin, water cooled shaft drive.  That bike still has an active and devoted on-line user community now, and with that support many people are still able to keep their 40 year old bikes in use.  The group support is  incredibly helpful, and really enhances the enjoyment also. 

I agree that spending $525 to have a perfect tank on a bike worth maybe $2000-$2500 (and I only think that much because this one is pristine and has only 3000 miles) is not a smart play.  But you know, boys and their toys and the desire for the toys to be nicely kept.  I have a buddy who spent $125,000 on a restored 1940 Stearman biplane (it was like new).  It was an open cockpit draggy plane (unflyable except in real good weather) that cruised about 95mph on 300HP (you are burning 15 gallons of $5 avgas to go 100 miles).  My much sleeker 1946 85HP enclosed cockpit Cessna 140 cruised 105mph on 4 gallons an hour, and only cost me $3500 for a one third share.  My wife and I had at least as much fun for $3.5k in that plane as my friend had for $125k.  But, he loved his special classic, and sometimes it's about emotion more than practicality. 

I would like that "perfect" tank, but being a practical guy whose gas tank is only mildly corroded (maybe the gas treatment is really slowing the corrosion down) I am thinking I may first try the amateur muratic acid treatment and a clear fuel line with filter to monitor the color.  If the fuel going to the carbs does not stay clear, I will probably spend for the professional lining.

Gruntle, you are right that it is a lot of discussion to try to get to the bottom of how to keep the carbs clear with minimum effort.  But,  some of the other guys also must think it is worth the effort, since they have taken a lot of their time to share their experiences.  For us, and especially for a less mechanically knowledgeable owner such as myself, I guess part of the enjoyment is figuring things out.  In this case, the tank corrosion problem affects a lot of owners, and not just ones that are not riding much.  Buddha has apparently lined a bunch of tanks, and we would not have gotten the benefit of his experience using different products and methods without discussion.  The outfit I mentioned above, Motorcycle Fuel Tank Lining Services, says that they have restored 770,000 gas tanks in 43 years of operation.  This problem is so on-going even today that it is keeping 19 guys there employed full time.

I had a similar long thread on here about exhaust header bolts--I think about 50 replies on that simple subject.  Some of the guys use stainless steel in preference to the OEM zinc plated steel, and recommend it strongly so that old bolts don't shear off.  I ordered some stainless steel studs and bolts to do that.  But, after looking into the material science (I went so far as to contact an old friend who is a PhD in material science and a corrosion specialist), it became clear that aluminum is galvanically sacrificial to stainless steel.  Stainless steel bolts or studs will eventually destroy the aluminum threads in the engine block.  Race engine builders regularly use stainless steel bolts in aluminum engines, but race engines get burned up and don' have to last many years like we would like our GS500's to last.  Aluminum bolts would solve the corrosion problem, but people tend to break them off, and they are about 10X the price of the $3 standard bolts if you can even find them.  So, Suzuki was completely correct to use zinc plated steel bolts where the zinc is sacrificial to the aluminum, but nobody knew that because the shop manuals never mention it, and the high performance engine builders (whose engines don't have to last) do recommend stainless steel and generate the idea that it is what the "pros" use.  But, for a long life motorcycle engine, the best you can do is to simply change your zinc plated steel exhaust header bolts every few years before the zinc leaches away and the steel bolts then corrode so much that they are at risk of breaking.  So, it turns out that very minor sounding subject was worth some homework and a thoughtful conversation.  This gas tank issue is similar, with a lot of details to hash out before you can come to a valid conclusion.   

How are you gonna prove the coating is off here or there or whatever.
Mathematically in 5-8 yrs they're counting on the fact that 99% of bikes will have died or sold from unrelated causes.
I made some errors and still got 8+ yrs out of a POR15 coating and If I had taken a bit better care of it, may have lasted longer.
I need to fix it again and make sure I don't screw up and maybe install a 0 drain.

The chemistry is pretty sound - its the implementation that destroys them.
Perfect removal of rust, perfect drying without flash rust, perfect adhesion, perfect drying and exact amount of por15 and perfect thickness coat = 10+ yrs - on a tank I powdercoated after I did the coating. Coming to think of it you can measure the surface area of the tank, and have the thickness speced out and know the shrinkage and dilute the coating to fully coat all surfaces with its flow rate etc etc etc you should get a coating like I did with 0 drain.

BTW 0 drain is where you weld up a tube on top of the tank with a drain hole, then you put one of em freelo 1 way valve hoses on. Added benefit, it wont need the cap to vent it, and wont get choked off by a tank bag.

Cool.
Buddha.

Quote from: Bluesmudge on May 07, 2020, 03:59:14 PM

Quote from: The Buddha on May 07, 2020, 03:13:44 PM

The GS tank isn't likely to last over 5-6 yrs unless you make it a 0 drain - or are very very lucky. He's counting on the fact a GS in 4-5 yrs will be either tossed in the trash, or sold, or ctually, all bikes get sold in 4-6 yrs anyway.

WHat? I've had my GS500 for 12 years. I've never done anything to the tank except run gasoline through it.

Same here... Not to stir the pot, but is this problem really a "thing" that lots of riders deal with?  All my GSs, including my '82, never had any work done to the tanks, other than exterior paint (strictly for aesthetic reasons).  I did give one of them (can't remember which one) the "put in a chain and shake the heck out of it" treatment to remove what I perceived to be a bit of surface corrosion when I had it painted a few years back, but have never had a tank problem.  What's the culprit... lack of riding, crappy gas, humid environment?  I use ethanol treatment regularly (or non-ethanol gas since I am lucky enough to have a station close by that sells it)... does that make a difference?

Earlier - in fact the early 80's Hondas were the best, followed by kawi and Suzuki and then Yamaha had nice electro galvanized tanks.
Those suckers don't rust unless you left em in the rain.
GS500's OTOH are terrible. Tank, frame everything will rust.

Cool.
Buddha.

To answer Bruce's question, the tank corrosion does seem to be a real thing.  If it was not, Motorcycle Fuel Tank Lining Services in Florida would not be derusting and lining 80 tanks per day.  The owner says they are working two shifts a day 7 days a week to keep up with demand.  And, those over 25,000 tanks a year they are restoring are only a tiny fraction of the tanks that need it. 

My own tanks is like Bruce's in that it only has a light layer of corrosion.  I also keep gas preservative in it through the winter when the bike does not get ridden much, which may be helping to limit the corrosion. 

Still, my carbs (which were fine last November, the last time I had the bike on the highway till April) are apparently about half gummed up this spring.  So, my question was whether that is varnishing from the fuel (despite preservative, a few winter rides, and some idling in-between to flush the carbs), flakes of corrosion from the tank washing into the carbs, or both. 

That could be pretty hard to accurately attribute to each source.  So, it seems I should attack both sources.  Once the carbs are cleaned out again, add an On/Off valve feeding the carbs so that if the bike is parked for a while, I can take just a minute to run the carbs out dry (no gas, no varnish to settle out, should be no problem unless the metal parts can rust).  And, keep the gas treated and also make a point to run the bike more.  For the tanks, at the minimum derust them on a schedule (maybe once per two years), or get the tank lined. 

Buddha seems to be saying the nearly zero failure rate reported by the professional services is partly due to the fact that the bikes are sold or removed from service so that the lifetime warranty does not get used.  But for owners who KEEP the bike, that lifetime warranty means that even if you have a tank liner failure 10 years down the line, they will repair it for free.   So, even though it is about $500-$550 with shipping, it is still pretty close to a guaranteed permanent solution so long as the shop stays in business.   

Buddha has done the tank lining multiple times and is probably getting pretty good at.  The rest of us generally have not, so doing it ourselves is a bit risky--according to Amazon reviews about a 10% bad failure rate, and another 10% that is problematic.     

Another option might be to find a local shop with at least moderate experience (which is a whole lot more than most of us) and let them do it for you.  The last time I had my tank derusted a few years ago was $85.  That may have been just a muratic acid wash.  Maybe a more thorough local cleaning worthy of a liner is $125.  If it takes them $30 worth of materials and 2 hours of labor at $60/hour to line the cleaned tank, the total is about $125+ $30 + $120 = $275.  That's about half of what the professional tank restoration shops plus shipping will run, and probably a better job than a guy doing it for the first time can do.  So, if $500 to $550 for a pro job with lifetime warranty is too much, and the owner is not sure he can do a good job himself, maybe that is a good compromise. 

Back when I had a very talented tig welder, I'd cut open the underside of the tank, de dent them by bashing them out from the inside, and coat everything by hand and paint brush till about 2" around the cut.
Then since the cut was straight below the filler cap, I could paint it with a long brush as well.
That would be an awesome way to do a coat job, except the tig welder is long busted and he's given up and quit welding as a side business.
Ask the guy if he's done a GS tank. I'll bet he hasn't however if you had a good vacuum to suck the excess anything out from the tank you will likely be good coating it without cutting or making a vent/drain. The key is to get it dry and get excess coating out as quickly as possible when the job is done.
Yea make some industrial strength vacuum cleaner and suck it out when needed. That's about the best option IMHO.

Cool.
Buddha.

Too bad they don't make these tanks out of aluminum.  I had an aluminum gas tank in my 1946 Cessna, and at 60 years of age it was still perfect. It is also a popular tank material for trucks and for replacement tanks in classic vehicles.  Aluminum does oxidize, but the oxidizing forms a non-flaking smooth surface that is very tough (it is the second hardest material after diamond), so it sticks on and will not contaminate the fuel system.  As the layer forms, the rate of growth slows to near zero, since it protects the underlying aluminum from exposure to oxygen.  Aluminum aircraft now over 80 years old are still perfectly sound.

 

There is a another point I can make about the commercial tank lining services.  They are generally claiming that less than 0.1% of their tanks per year come under the warranty, and far less than that for the highest volume outfit Motorcycle Fuel Tank Lining Services. 

It is true that most bikes do not have extremely long service lives or get sold, so that the lifetime warranty service is never requested. 

But, the failure rates are SO low that even when this is taken into account, actual failure rate remains low.  For example, assume 90% of bikes are retired or sold before failure ever becomes an issue.  Then the 0.1% apparent failure rate is only being measured on 10% of the bikes--the actual failure rate would be 10X this amount.  But, that is still only 1% per year for old tank linings, and apparently lower than that for the porcelainizing (ceramic glazing) process used by Motorcycle Fuel Tank Lining Services.   

Given that the odds of having a failure are this low on these professional linings, and that they will fix it free if it does have a failure, the professional lining is a good deal for a highly appreciated bike that an owner plans to keep many years.