If Only a New Gas Tank were an Option...
Rusty McRusterton
I had set the gas tank and it's cap up for electrolysis (something I had never tried before). First off, I ran into a few issues, nothing major, just continually frustrating.First issue: After putting the steel shank in the tank the charger kept faulting; it would read "Trouble." So I decided to take that piece out and just use the rebar sitting outside of the tank. I kind of figured this wouldn't work too well because I'm fairly certain the rust has to have a pretty simple path of travel (a "line of sight") for the process to work best. The shank removal seemed to help and eventually, while the process was running, I brought the shank back in and set it of floating above the outside of the tank and it worked a little.
Second issue: The charger (1.5 amp with 6V/12V switch and safety off)
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| Motorcycle Trickle Charger |
Another Round of Electrolysis
Since my first run through of electrolysis was marginally successful, I decided to get a bit more creative on the tank. The gas cap cleaned up pretty good so I left that out for the next attack. |
| 1975 CB750F Gas Cap (Top) |
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| 1975 CB750F Gas Cap (Bottom, no gasket) |
I disassembled my whole setup, dumped the rusty water, and prepared to setup again. There was definitely rust removed after the first round just not nearly enough. This time, I needed to get something in the tank. I came up with a plan.
I took 2-12" pieces of rebar, then found PVC caps in the plumbing section of Home Depot that would fit snugly on the end of the rebar with the help of a couple taps of the hammer; these caps would keep the rebar from touching the inside of the tank. I then wired them together with insulated electrical wire so that no wire would be touching the tank but one could lay on each side of the inside of the tank. From that setup I then ran another insulated wire out of the tank off of one of the pieces of rebar. The setup:
I tried to insert this in the tank but it turned out that the 12" was a bit too long. I ended up tanking a hacksaw and removing about 4" from each bar and they slipped right in. From here I got the process setup again and ran it.
Overall, this seemed to work decently. I ran into the "Charged" issue again so I would let it sit unplugged for half a day or so then plug it back in to do its work. To give you a time frame, I was really casually running this during work and sleep while adjusting after work for several days. Being that the process didn't execute perfectly like all the YouTube videos, I can't tell you how long it really took and the overall efficiency was pretty low. That being said, I will use this process again in the future, just hopefully never on a gas tank or any mostly enclosed vessel.
After this round, I decided "good enough" because it had seemingly done all it could and I knew other measures had to be taken. We'll get to that later.
Let's Get to those Carbs
As anyone can tell you when it comes to motorcycles that have been sitting, flush the fuel and clean the carburetors at a minimum, and, generally, you'll have to do something to the tank too (ya think?). I had previously taken the carbs apart but left them to the side for a while.
I took all 4 carbs apart separately and set them in individual areas to try and keep the parts together. I removed all of the pilot jets, main jets, float needles, and float pins for all 4 carbs and piled them together for carb cleaning. I then took a plastic dish I got from the dollar store and sprayed enough carb cleaner in to soak all the pieces.
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| Jets, Float Pins, and Needles Soaking in Carb Cleaner |
I left this sit with a lid on it for a few days.
WARNING: If your float needles have rubber tips, DO NOT do this. Carb cleaner eats rubber and you will need new float needles.
I didn't think about this until after they had been soaking for a while but luckily my float needles had no rubber.
While this was soaking, I started to look at the carburetor itself. I sprayed it a bit and scrubbed with a toothbrush and a brass brush. The varnish was really not coming off well. This was not only going to take forever but also looked like it might not get the job done. I decided to do some research online.
After investigation, it turns out that the only way to clean components like carburetors (and seemingly everything else), is ultrasonic cleaning. Great. Something I don't have and that will probably cost hundreds of dollars. After checking Craigslist, yup, hundreds of dollars. Eventually, I found one at Home Depot for around $35 and ordered it. I knew it would be small but it was cheap.
I got the ultrasonic cleaner and tried it out at home.
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| Tiny Ultrasonic Cleaner |
This thing was TINY! In the picture on the left is the float bowl for one carburetor. This was just too small and didn't work very well so I returned it. There was no way I was going to be able to get my carbs clean with that. Don't buy one of these.
I did a bit more research and found a great ultrasonic cleaner from Harbor Freight. It was $80 on sale then I used a 20% off coupon that you can find under a rock just about anywhere (or in motorcycle or handyman magazines). Luckily I had a gift card from the in-laws to use there too :). This unit is way bigger and has heat to aid the process.
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| Proper Ultrasonic Cleaner |
The Process
For each carb, I fully disassembled the carburetor (jets, needle, slide, floats, air mixture screw).Note: when removing the air mixture screw, bottom the screw out (clockwise) and count the turns that it takes to do so in half turns (1/2, 1, 1 1/2, 2). This will need to be set when re-installing.
I then filled the cleaner with water and added Simple Green in heavy concentration (no specific measurement). The ultrasonic cleaner runs at max for 480 seconds, so I set it to the 480 second cycle with heat turned on. I ran this process for just over an hour on each carburetor, replacing the solution between carbs.
When pulling components out, if they were still dirty the went back in for another round. If they were clean enough, they were rinsed with water and blown out with an air compressor. This process worked VERY well.
Before:
After:
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| 1975 CB750F Cleaned Carb |
Before:
After:
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| 1975 CB750F Carbs Cleaned (From Air Box) |
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| 1975 CB750F Carbs Cleaned (From Air Box) |
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| 1975 CB750F Carbs Cleaned (To Engine) |
The pictures don't do it justice and the one carb shown open in the pic is the worst out of them all inside. The process worked amazingly well. If you ever need to clean carbs or anything of the like, buy that unit! The heat really helped too.
After cleaning all of the components, do a few checks:
- Ensure you blow out all passages with 120 psi compressed air
- This means pilot jet, main jet, fuel delivery, overflow, breather
- For passages with no rubber, shoot carb cleaner through and ensure it comes out the other end properly
- For needles, ensure all holes are round when looking through the needle at light. Carb cleaner has a hard time getting hardened (calcified?) junk out. This may need to be cleaned out manually or the jets may need to be replaced. I had to use a small needle/pin on my pilot jets to clear out some hardened material.
With the carburetors reassembled, I was just missing some very very small split pins that hold the choke linkages in place. They are about 1/32" so no where had anything of the sort. I ended up just creating my own out of a small, less than 18 gauge, wire. Carbs are good to go.
What's the Deal with that Tank?
After the electrolysis, I realized that there was more to the inside of the tank than I had thought. Although rust had been removed, it appeared that there was still a white sediment. Upon further investigation, it turned out that it was not sediment but a previous tank liner. I'm not sure whether this was from the factory or done by someone later on. In any case, another headache was born.
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| 1975 CB750F Fuel Tank with Cork for Chemical Treatment |
Bits of the liner were flopping around inside the tank which meant that it had to be removed so that it wouldn't clog the filter later on. To start, I filled the tank with 100 small nuts and the 2-4" pieces of rebar that were cut off previously. I then created a plug for the fuel delivery hole with a wine cork that I shaved down. 
Next, I inserted 2 quarts of lacquer thinner.
The idea is that the lacquer thinner breaks down the liner chemically while shaking the chunks of metal around knock the pieces loose inside.
I spent the next several days shaking everything around in various ways. Then when a chunk of liner would come near the opening I would grab it with some needle nose pliers. After a while I had quite a pile of what appeared to be dead animal skin.
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| Old Tank Liner |
Unfortunately, this was not even close to all of it. I later fashioned a hanger into a scraper/hook and pulled out more and more. By the end of my extensive efforts, I got most of it all out and the rest seemed to be stuck in some seams in the corners. Being that I planned on putting a tank liner in, I figured these would get sealed over.
I drained the lacquer thinner and removed the nuts using an extending magnet. I then poured acetone in for a last aggressive wash around in the tank. After letting the acetone sit and then slosh I drained it. The tank then needed to dry to be able to put the liner in so it would sit for a couple of days.
The Liner
After letting the tank sit, to dry, I was ready to put the liner in. I had rolled a liner in a tank before so I was familiar with this part. Previously I had used Kreem. After some research, I found that Red-Kote gets much better reviews. As such, I went with Red Kote (can be ordered online or at O'Reilly auto parts stores). I poured the tank liner in and started sloshing it around in the tank.
The main difference with Red-Kote (besides it being red) is that it's an acetone base. As I poured it through the tank, the excess that was draining was not what I was hoping for. Additional bits of that previous tank liner were coming out. Evidently, the acetone that I had previously used was not strong enough. As such, the Red-Kote was breaking down more bits of liner that I didn't even know were in there and making a mess inside the tank. NOT GOOD.
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| MEK (MethylEthylKetone) |
After running this through the tank in about 5-6 washes, a LOT more of the liner bits had come out. I think now the tank is better prepared for a liner. Unfortunately, I had to order a new liner because the other one now had some dissolved crap in it.
So, from here, hopefully all the loose junk will be out and the liner will work and I can get this tank on the bike.
WHAT A MESS!!!
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