Topic: Marissa's 1972 CB500

[onepieceatatime]

I cleaned mine with a diluted acid (CLR type product) and a handful of drywall screws before I used Caswell. The  rinsed with several flushes of clean water and a rinse of acetone. Once that was dry I used the Caswell. I would also probably clean your tank more, if it was mine, to get rid of the darker brown rust that is farther down in your tank first. the lighter rust near the top is more what mine looked like before sealing. I'll try to remember to take a picture inside the tank next time I get to my storage garage, as that is not one of the bikes I currently have registered.

[RAFster122s]

A forced air drying can help get the tank dry inside before you start the liner. Many will use a hairdryer to blow in the filler neck on no heat for several hours to dry out the tank.

Theoretically the acetone is to combine with the water, but this only happens when you do not have porous rust capturing the water.
I think you have more rusty scale to get out of the tank before you line it. I believe you would trap water in that rust and it would continue to rust beneath the liner until it eventually ate through the steel and began leaking. Often to help break the stuff free you will need to add a length of chain into your tank to provide a mechanical means of breaking it up.  Filling with a liquid and your chain and then lots of agitation to break up the rusty scale.
Not using a chain that is so heavy it is going to dent up your tank but heavy enough to break up the rusty scale...yeah, I know not real specific on size.

My $0.02

David

[DaveBarbier]

Yeah, that’s not surface rust, that’s just rust. Flakey deep rust. You need to use an actual rust remover like Metal Rescue or the equivalent. First use water with screws or nuts and bolts or a chain and slosh the hell out of it. Just count the number of screws you put in so you know you got them all out.

[Bankerdanny]

Stop using water. You’re defeating your intentions. Use MetalRescue or similar. This will leave a protective finish that will discourage rust. Then line it if you wish. You really only need to line a tank to resolve holes in the metal. Rust is easily treated and properly done, you should have no further occurrence.

+1. The failure rate for liners is high. Not because the liner material itself is bad, but because prep is so important and even diligent owners can screw it up. If you don't have holes I just don't see that a liner of any brand is worth installing.

In 2011 I used a water/baking soda mix as a rinse/acid neutralizer post The Works toilet bowl cleaner treatment on my 550k then followed up with denatured alcohol to dry the tank and then Marvel Mystery Oil to coat and prevent flash rust. It worked well, and protected the tank for the couple days I needed before I added fuel.

I get why avoiding water is desirable, but a hose and high pressure water from a sprayer helps make sure all the loose rust get flushed out. The alcohol rinse immediately after helps dry the tank quickly to limit flash rust before the MMO can be applied to protect the surface.

[SF]

Plus 1 on metal rescue......fill it and let it sit while you work on the bike, giving it a shake and a turn every few days.


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[HondaMan]

If you'd like to do it once, and forever, and stop any 'almost leaking' seams, spring for the POR15 kit. You must remove the fuel petcock, then grease up 2 screws longer than the ones that mount it and screw them up into the petcock holes before lining: I recommend installing a small piece of roof flashing (or other similar thin sheet metal) with a piece of waxed paper between it and the tank, over the petcock's hole. Then do their 3-step kit and let it dry at least 2 days where it says, "let it dry well". This stuff makes a liner that is impervious to ANYTHING, about 0.060" thick, and it will make a little sealed housing over those extra-long screws you put into the petcock holes. Then when you pull them out, it leaves a sealed shroud over the tips of the screws that mount the petcock, further aiding in preventing future leaks. The kits are pricey, but IMHO worth every cent.

[dave the welder]

her is my 2cents worth on tank liners. I used Redcote? several years ago. followed direction to the letter. no problems ever. the only thing I noticed was the first tank or so the fuel had a  slight red tinge. it did not hurt anything and was gone by 3rd tank. every one  has  there opinion on this  stuff what ever you use follow directions EXACTLY as printed and life will be good

[Godffery]

 + 1 on the POR-15 product.
I build at least one er two custom Fuel Tanks a year and use there products exclusively for the sealing.

[rb550four]

Prep is key. I use the nuts and bolts method first every time, just because the bottom of the tank doesn't have flakey rust doesn't mean isn't happening on the inner top where the air is....like cast iron waste pipes, they rust out from the top where the air is ,not where the liquid lays.  Have used toilet bowl cleaner or Evaporust does the job but the flash rust is a concern unless  you use alcohol as a dryer. My favorite is gin with a little tonic and Tom Collins mix with a slice of lime, it make this  dull job seem interesting, but the tank gets rubbing alcohol and when it's dry POR15. I don't like the tank mix because it's too thin and I feel that it needs a second coat ....the best part of the POR15 tank mix is that it comes in grey. The black POR 15 for frame restoration is what I like to use , seems to be thicker when dry if you leave  too much in the bottom it can dry crackley. The only draw back on the black is that it's hard to see the fuel level inside.
  It's a good product for battery trays as acid doesn't seem to effect it. The only thing that can wreck POR15 is sunlight it seems.  So it's good in a dark tank . I never use it on MC frames because sunlight dulls out the gloss on my truck frames.

[Godffery]

 I'll second that "Prep is key" statement, also not letting it puddle anywhere. (that apples to any brand coating you choose to go with)

[DaveBarbier]

With all this talk about liners, I still say to slosh the #$%* out of it* with water and nuts and bolts to remove the heavy rust and then metal rescue or similar after to remove the rest. Only line if there are pinhole leaks.

* I’ve heard of people putting the tank in the dryer wrapped in blankets with no heat with nuts/bolts or maybe a couple fist fulls of pennies so it’s less damaging. No liquid, rinse it out after the dryer.

[theDQG]

With all this talk about liners, I still say to slosh the #$%* out of it* with water and nuts and bolts to remove the heavy rust and then metal rescue or similar after to remove the rest. Only line if there are pinhole leaks.

* I’ve heard of people putting the tank in the dryer wrapped in blankets with no heat with nuts/bolts or maybe a couple fist fulls of pennies so it’s less damaging. No liquid, rinse it out after the dryer.

White Vinegar would be much better at dislodging and breaking down rust than water. I'd use about a 3' to 4' light chain, zinc plated over nuts and bolts because the chain bundles up and contacts more surface than nuts and bolts do.

If you do put in nuts and bolts, better count them first!

[DaveBarbier]

With all this talk about liners, I still say to slosh the #$%* out of it* with water and nuts and bolts to remove the heavy rust and then metal rescue or similar after to remove the rest. Only line if there are pinhole leaks.

* I’ve heard of people putting the tank in the dryer wrapped in blankets with no heat with nuts/bolts or maybe a couple fist fulls of pennies so it’s less damaging. No liquid, rinse it out after the dryer.

White Vinegar would be much better at dislodging and breaking down rust than water. I'd use about a 3' to 4' light chain, zinc plated over nuts and bolts because the chain bundles up and contacts more surface than nuts and bolts do.

If you do put in nuts and bolts, better count them first!

The water would just be to keep the rust in suspension. I don’t like the idea of adding an acid especially when you’re going to use metal rescue anyway. The mechanical process of the nuts/bolts/chain/pennies is really what’s going to get the flakey rust off.

For sure, count whatever you put in there first!

The more I think about it the more I like the chain idea or the pennies in the dryer without any liquid. Then finish off with metal rescue.

[theDQG]

The water would just be to keep the rust in suspension. I don’t like the idea of adding an acid especially when you’re going to use metal rescue anyway. The mechanical process of the nuts/bolts/chain/pennies is really what’s going to get the flakey rust off.

For sure, count whatever you put in there first!

The more I think about it the more I like the chain idea or the pennies in the dryer without any liquid. Then finish off with metal rescue.

Yes, vinegar is mildly acidic, but it will dislodge stubborn rust. Water won't do that. When you're done, just rinse out with baking soda and water, then 99% iso alcohol to minimize flash rusting. Best part of this is that all ingredients are biodegradable- you can just dump everything out in the backyard.

I used this zinc-plated chain from ACE hardware, and my tank went from a rust bucket to the one you see in the pic below.

[BenelliSEI]

Seen a few discussions on cleaning out gas tanks, here’s my 2 cents worth...... read this years ago, tried it and it’s my “go to solution”.

First problem with an old tank is really getting out the old gas. Methyl Alcohol will remove old, dried up gas. Commonly sold as HEET, it makes water soluble in gas, but also melts out the dried crud. Slosh it around, it does a good job. Dump it all, dries quickly. Next, visit any good FARM SUPPLY STORE and ask for Stearns Milkstone Remover. Milkstone Remover (MSR) is about 75% phosphoric acid. Typically diluted and used for cleaning dairy equipment. Last gallon I bought was a different brand, labeled “Super Dicoloid”. The guys on the counter will know, about $20.

I have a large Rubbermaid container (with a lid). It easily holds eight gallons of water. Add the MSR to the water (NOT the other way around). From that brew, fill the tank to the brim, and leave it somewhere warm for 24 hours. After you pour it back into the tub (I keep it for years), you will be amazed at the results. Want it cleaner? Do it again. The tub is great, you can hang any old bits in for a good cleaning too (after removing dirt an grease). It works for ages and when it loses it’s effectiveness, dilute it with more water, and fertilize your lawn...... no stink and it doesn’t hurt Chrome. If you get any on your paint, just dilute with water and wash off.

When finished, I rinse out the gas tank with warm water and then shake a mix of HEET and two stroke oil around, to stop any flash rusting. I never use a tank liner. If your tank has a leak, fix it properly.

[jgger]

Marissa,  you have not posted in awhile,  I hope it's because everything is sorted out. Have you been out riding and keeping it a secret from all of us? Feeble old minds want to know!🤔

[Marissa]

Well I went ahead and tried the metal chain trick with evaporust, soaked the tank for a full day and put it on its side, upside down, etc. to remove the rust. Seems like it had done a fairly good job! And it took out a lot of gross scaling.

Dried out the tank with a gallon of acetone and I also used that as the "wash" to remove the scaling and big pieces of rust. I had a fine woven hand cloth as a filter on top of a funnel so I'd empty it from the tank, back into it's container, then back into the tank. I did that like 7 times. After I left it dry over night, I checked it the next morning by shaking it to see if I head anything else and not really.





 This was the only area I found surface rust on, but seemed really light so I'm not concerned about it.



Here's what came out of it.









My set up.


Friday, I poured in the liner. I am still waiting for it to cure, Caswell says anywhere from 3 - 5 days for cure time, so I am going to wait a while before I see if my job was a success. Overall, it was pretty straightforward. My only worry is that there are bubbles that formed in the surface of the liner, which none of them seemed to have popped, but I'm worried this might lead to delamination or something. Not sure if that's just how it applies and maybe is normal.

While I've been waiting, I got the bike to start up almost instantly Saturday morning. My tach cable was not attached correctly so I couldn't see idle speed but it was definitely high. I took it down my driveway anyways and down the block for some testing. At some point, about halfway through my test ride, it start to bog with throttle and then it died which was weird. So I started walking it back and letting it cool, then once I got to a downhill area I started it back up and got to ride it the rest of the way home. I'm not sure if that was just a fluke or what. Then, I put my left engine cover back on and accidentally crimped my oil pressure wire, so I looked down during the second test ride and saw that my oil light came on, freaked out, but saw no trail or oil and smelt nothing so I just took it back home quickly and checked. That was a silly mistake but an easy fix. The last thing I did was go to synch the carbs, for some reason #3 would not adjust at all, regardless if the set screw was in or not, so I have to take a look at the linkage and see if it needs adjustment. However one of the videos I was watching online said Honda considered them within spec if they were half an inch off. So perhaps this is no big deal for now.

The highest gear I could get it in was 3rd, I think the fastest I went was about 40 yesterday. I have a feeling that 4th and 5th are just not engaged correctly which is frustrating, but for one season I can live with just backroad gears. I don't know if maybe I have to be at a higher rpm and speed to get the bike into those gears but I'm doubtful it's anything like that. If anything, I'm just impressed I somehow messed that up even though I followed a video and have 1, neutral, 2 and 3 perfect. Lol.

Next on the list is likely new spark plugs so I can keep testing, new throttle cables, and a new gas tank seal. I bought shorty throttle cables from 4into1 and for some reason I can't get the cables to stay on the carb end. Coming down from throttle one of them always disconnects because there's too much slack. But I have them set up like OE spec where they cross over onto the left side of the frame. So I'm unsure if I should buy shorty ones again or buy OE and have really long cables but maybe they'll have less play in them.

[DaveBarbier]

Cool, tank looked clean. No idea about the bubbles in the liner but I hope it all works out.

For your ride what were you using for a fuel tank?

Were able to get a strobe and dynamically time the ignition?

[Marissa]

I have a plastic quart jug used for carb synching and stuff like that. I also have not dynamically timed the ignition yet.

I broke down today and gas started pouring out of carb #3. Also, today two funky things started happening:

#1, my neutral safety light started working intermittently. When the bike was off but power on, it wouldn't light. Then, if the light was on while the bike was running, as soon as you shifted it into one of the gears and back into neutral, it wouldn't light up again.

#2, this one has me dumbfounded. No throttle, in neutral, choke closed and the bike is fully warmed up. I was coasting downhill in neutral coming to a stop when I see my bike is hanging onto 4,000 rpm. My throttle cables were slacked, the choke was not touched, I wasn't doing anything. It also wasn't fumbling either. It was just revving on it's own.


So I ended up losing all of my gas and had to walk it a 1/2 mile back to my house uphill. Luckily, my brother came to help, as well as one of my neighbors who has a teal Tao Tao, lol.

[HondaMan]

I have a plastic quart jug used for carb synching and stuff like that. I also have not dynamically timed the ignition yet.

I broke down today and gas started pouring out of carb #3. Also, today two funky things started happening:

#1, my neutral safety light started working intermittently. When the bike was off but power on, it wouldn't light. Then, if the light was on while the bike was running, as soon as you shifted it into one of the gears and back into neutral, it wouldn't light up again.

#2, this one has me dumbfounded. No throttle, in neutral, choke closed and the bike is fully warmed up. I was coasting downhill in neutral coming to a stop when I see my bike is hanging onto 4,000 rpm. My throttle cables were slacked, the choke was not touched, I wasn't doing anything. It also wasn't fumbling either. It was just revving on it's own.


So I ended up losing all of my gas and had to walk it a 1/2 mile back to my house uphill. Luckily, my brother came to help, as well as one of my neighbors who has a teal Tao Tao, lol.

The 'hanging idle' is real common on the 550 when the carbs are running richer than they should. It is partly caused by the too-soft spark advancer springs (which you should trim back at some point for better all-around performance, and cleaner plugs). The fuel builds up as wet gas on those cast intake runners, and when you close the throttle it still gets too much fuel, until it finally burns some off. Annoying, but 100% fixable! Trim 1/2 turn off one of the advancer springs (eventually you'll want to do both) and re-bend the end of it out to hook back into the advancer weight.

The light: the little spring for the Neutral switch is probably rusty. It's not a great connection to begin with, being where the chain goo can get to it and make it stop working from time-to-time, but good maintenance will keep it working well. Just clean the rust off the spring (and the little washer, if yours has one of those, some don't ).

It sure sounds like you might need a different carb body, or something? I have some odd 550 carb parts lying about, which number are yours? And, is it the #1 carb?

[DaveBarbier]

I have a plastic quart jug used for carb synching and stuff like that. I also have not dynamically timed the ignition yet.

I broke down today and gas started pouring out of carb #3. Also, today two funky things started happening:

#1, my neutral safety light started working intermittently. When the bike was off but power on, it wouldn't light. Then, if the light was on while the bike was running, as soon as you shifted it into one of the gears and back into neutral, it wouldn't light up again.

#2, this one has me dumbfounded. No throttle, in neutral, choke closed and the bike is fully warmed up. I was coasting downhill in neutral coming to a stop when I see my bike is hanging onto 4,000 rpm. My throttle cables were slacked, the choke was not touched, I wasn't doing anything. It also wasn't fumbling either. It was just revving on it's own.


So I ended up losing all of my gas and had to walk it a 1/2 mile back to my house uphill. Luckily, my brother came to help, as well as one of my neighbors who has a teal Tao Tao, lol.

The 'hanging idle' is real common on the 550 when the carbs are running richer than they should. It is partly caused by the too-soft spark advancer springs (which you should trim back at some point for better all-around performance, and cleaner plugs). The fuel builds up as wet gas on those cast intake runners, and when you close the throttle it still gets too much fuel, until it finally burns some off. Annoying, but 100% fixable! Trim 1/2 turn off one of the advancer springs (eventually you'll want to do both) and re-bend the end of it out to hook back into the advancer weight.

Mark, this can be verified with a strobe, right? Marissa hasn’t yet dynamically timed the ignition so I would first time it then see if the advance comes in too early.

[Farley121]

  HondaMan,

How far up does cutting the springs raise the "all in" of the advance?

[HondaMan]

  HondaMan,

How far up does cutting the springs raise the "all in" of the advance?

The first 1/2 coil cut off usually slows the advance to around 1800 RPM or so, if it is hitting full advance by 1500 (like most are that I have seen in the last 10 years). This causes much trouble...cutting half off both springs can delay it toward 2000-2100 RPM or so. For the 500/550 intake tract to "meet" the intake flow and cam timing, the full advance should not come on until 2500 RPM, but I find that 2700-ish works better yet, and keeps the plugs cleaner. The 750 is similar: I had mine at 3000 RPM full advance from 1977 until 2018, at which time I installed one regular spring again to do some more experiments with my freshly-rebuilt engine. Currently it is advancing full by 2200 RPM, and it is much too soon, causing increased plug fouling in heavy, slow city traffic riding. When I have some time I'll cut off 1/2 turn from the new spring, trying for 2500 RPM with the new jets I just installed last month, etc.

[Farley121]

Thats great, thanks for the reply.

[Marissa]

Bike is quite rich, trying 100 main jets next.



While I was replacing the gas cap seal, I found a weird buildup of sort. Looks like old tank liner or maybe dust covered varnished gas? I'm not totally sure.




A little under the weather today. Perhaps I can test it tomorrow.