Fuel Tank, Brakes, and Electrical

Finalizing the Fuel Tank

After enduring an extensive amount of trials on the fuel tank, it looked like it was finally getting closer to a tank that could be used to hold fuel.  As mentioned previously, I had to find the most aggressive solution possible to tackle the remains of the old liner as well as, now, the new liner that I had rolled in.  I purchased the MEK in a gallon and put that through the tank in about 5 or so washes.  This broke down the stuff inside just as I needed it to.  In the end, it didn't get everything so there was a little bit of the old liner left in the seams (this would be coated by the new liner).  In any case, it was prepped and I just had to let it sit so that it was bone dry and ready for the new (new) liner.

Red-Kote Fuel Tank Liner

After letting the tank sit for a few days to dry, I then put a vacuum hose inside and moved it all around just to ensure there were no loose pieces inside.  Finally, I was ready to put in the liner (for real this time).  As before, Red-Kote is the liner of choice.  The most notable difference that I could tell between this and the Kreem, physically, is that the Red-Kote seems to dry as a firmer shell whereas the Kreem seems to dry as a softer, latex-y type coating.  In any case, I plugged the holes like before and rolled the liner around inside the tank.  After rolling around, I drained the excess as required (with fingers crossed) and, gloriously, all that came out was the excess liner, no extras like before.

At this point, the liner needed to be rolled on every side for about 30 seconds to collect excess, then drain.  After going through this process for 40+ minutes, it appeared that no more was really draining meaning that there wasn't much in terms of pooling in the tank (which is what you want).  At this point it was left to sit until dry.

1975 CB750F Fuel Tank Opening with Red-Kote Applied

1975 CB750F Fuel Tank

You also might note that the tank is looking pretty rough at this state.  After all of the electrolysis, air blowing, chemicals, etc. it has taken a visual toll.  In any case it will be eventually be painted so for the time being, it's going to look ugly.

Front Brake

While the tank was drying, I decided to look into another issue.  When I first got the bike, there was no front brake lever and the rear brake seemed to have been blown; in other words, the bike had no brakes.  I installed the front brake lever almost as soon as I got the bike home.  The first time I grabbed the lever it stopped the bike.  The problem was that it didn't let go.  I ended up having to loosen the caliper to get the bike to move again.

I took the wheel off and removed the caliper.  As I did, the pads looked fine (not a real surprise) but the piston still wouldn't retract.  I pumped the brake a few times and the piston came out slowly.  Upon its extraction, I saw the issue at hand.  With all parts removed, I could see that water had somehow got into the caliper.  As a result, the brake pad, caliper, and piston all had rust and/or corrosion.

1975 CB750F Front Brake Caliper (Corroded/Rusted)

1975 CB750F Front Brake Caliper Piston Removed

I decided that I had to order new pads and an o-ring.  I put the piston and caliper into the ultrasonic cleaner (that thing is sure nice to have) to clean the components off.  Once I get the new parts, I will reassemble and it should work good as new.

Electrical

Crappy handlebars and controls

Back to the common theme of old bikes, electrical issues.  This particular year of bike had controls that were very annoying for a couple of reasons.  

1975 CB750F Left-Hand Switch

The first issue is that all of the controls are combined.  This means that on the left side the clutch and switches (hi/lo beam, horn, turn signals) were all in the same unit and on the right side the front brake and switches (starter, kill switch) were all in the same unit.  Because of this if you have an electrical switch problem or lever problem, the whole unit has to be fixed or replaced.  On a lot of newer bikes the levers and switches are separate.

The second issue that the the electrical wiring for the switches has no "out" when mounted on handlebars.  This means that the wires have to be run through a hole in the handlebars.  This causes a few issues.  One issue is that it's very challenging to cram all the wires through one hole and run down the bars and out another cramped hole in the center.  Because of this it can cause tears in the wiring insulation.  This also means that you're limited to only a few styles of handlebars because there aren't a lot that have holes built in.

Handlebars for 1975 CB750F

To add to the mess, the handlebars that someone had put on the bike were a fraction to small in diameter and it appeared that they did a haphazard job of putting the controls on.  As a result there were issues but we'll get back to that in a second.

The Electrical System

Battery in 1975 CB750F

In order to test the electrical system, I needed a battery.  I purchased and installed the new battery and switched the bike's ignition to "on."  When I did, there was life, but it sounded like very misguided life.  There was a blinker partially functioning, a buzzer making noise, and something clicking.  After about 10 seconds it stopped.  I decided to take a look at the fuse panel to have a place to start.

The main fuse had blown.  In addition, all of the fuses were extremely rusted and the placement within the panel was not correct.  I quickly made a new friend: the wiring diagram.

1975 CB750F Wiring Diagram

At this point I had to track down what had caused the blown fuse, whether it was 1 or 100 different things.  The first step was to get the fuse box properly organized.

1975 CB750F Fuse Box

There was one fuse holder missing and the main fuse was wired to a placeholder for a spare.  I took the box apart, brushed up all the fuses and their terminals, moved the main fuse terminal to the right spot and put it back to together.  I put the spare 15A (main) fuse in and turned it back on.  I got the same results as before and the fuse blew.  This being the case, I new it might start to get very costly and time consuming to track down an electrical issue.  If the fuse kept blowing, it wouldn't give me time to track the issue and I would also be buying tons of fuses.

If I was going to track electrical issues I had the option of replacing fuse after fuse but I really was looking for a better solution.  I kept thinking to myself, why can't there be breakers on automobiles just like houses?  I went to the auto parts store to get more fuses and look at my options.  Upon looking, I found something magnificent: a 15A breaker!  I was stoked.  I asked the guy at the store what it was for/how it worked and he had not clue.  The best part was that it said automatic reset so I new it was what I was looking for.

I removed the main fuse and wired the 15A breaker in place on the main fuse terminals.  Now when I turned the bike on, it did its thing but I was able to keep it on or turn it off and back on and keep working.

There was an array of areas to inspect.  Back in the day, there wasn't a lot of use of multiple wire connectors.  As a result, there were a lot of one-wire connections.

1975 CB750F Stock Wiring for Left Switch

1975 CB750F Wiring within Headlight Assembly

I decided to start with the left-hand switch because I had the blinker firing.  I had no headlight so that was another issue to track.  The blinker seemed to work but then tweak out in either left or right position.  I wasn't sure if this was an ignition switch issues, an issue with the passage from the main fuse, the head fuse, or the tail fuse, the rectifier, regulator, or what.  

1975 CB750F Gauges Removed

I got out my volt meter and started testing in combination with the wiring diagram to see where the current was running and if it was doing what the wiring diagram said it should.  I focused on the main components first.  Is there power crossing the main fuse?  Is the power going through the rectifier?  Is the power getting to the ignition switch at the proper voltage?  This meant I had to start exposing the terminals to test them so I had to take the gauges and ignition off.

1975 CB750F Ignition 

Once I validated that the ignition had the proper voltage, was it providing the proper voltage for the head fuse?  Was that traveling properly across the fuse?

After a bunch of testing, I determined that the issue must be the left control.  I disconnected the control and toggled the ignition and found that my issues were gone.  I then plugged it in piece by piece to see if it would trip the breaker and eventually it did.  I now knew that something was shorting in the left-hand switch.  I dismantled the switch and reveled that the wires running through the bars were in pretty bad shape.  There were too many areas that could have caused the short to make repairing the wires worth while so I knew I needed a new switch.

In the midst of testing the switch itself, I also ran through some testing as to why I had no headlight.  I tracked the power source as to what serves what function in the switch and determined that the blinkers were powered through the "winker relay" which gives them pulsed power but the headlight had to have an alternate, constant power wire.  I eventually tracked that to be the Black/Yellow wire.  Tracing the Bk/Y wire back to the fuse panel, I did some more testing.  The power seemed to be getting across the fuse but not from the fuse to the end of the wire that feeds the headlight.  I did some more testing and determined that the fuse end quality, as well as the terminals, were in too poor of a condition to properly conduct the current.  I cleaned all of the terminals with a wire brush and a light amount of WD-40 and replaced the 7A fuse.  This got me the power I needed for the headlight at the end of the wire.  I setup a direct connection to the headlight, bypassing the handlebar switch, and it finally worked.  Issue, resolved.

Replacing the Switch

Getting a new switch wasn't a big deal because I knew that I wanted to update the switches for more reliable electrical as well as the ability to have different bars (or clip-ons if I decide in the future).  I went to a bike junk yard parts type place that we have locally (Luckily.  These are not very common.) and started looking for a nice switch from Honda (to hopefully retain a close wiring configuration) that was from a newer bike.  In ended up getting one that was off of a 2004 VTR1000F (RC51).  The wires were pretty close but not identical.  Being that I had a new switch, I had to get a new clutch perch and lever too because the whole old unit was being removed.  I ended up finding one that worked from a 1987 CB900C.

2004 RC51 Left Hand Switch and 1987 CB900C Clutch Lever and Perch

Upon showing my wife the new switch she discovered that the horn button stuck in place.  Being that I was going to put this on the bike as a new reliable item, I had to determine the cause and fix it before trying to wire it to the bike.  I dissected the new switch down to the horn and found my issue.  The horn area had either been in an accident or the rider of that RC51 got pretty pissed off at someone and mashed the button in.

In any case, the mounting point for the horn contact was bent in pretty far and was letting the button push in too far and bind in the housing.  I straightened the mount but then there was another issue.  The contact point was held in place by very small, non-metallic rings so it wouldn't complete the circuit to actuate the horn.  One of this rings to hold the contact in place was broken and no longer functional leaving the contact floating and not secure.  This had to be replaced, otherwise the horn would be loose and potentially bind again.  Not only did I have to have something small but it couldn't be metallic, so no metal c-clip or wire.  I knew I would have a hell of a time trying to find something like this to purchase.  This is where I got creative.

I started looking around my garage to see what I could come up with; I needed a thick piece of plastic.  I eventually spotted thick plastic in the form of the casing for staple gun staples.  I clipped the corner off of the display tab and went to work.

I cut the size to roughly small enough for the application.  I then held the piece in pliers and drilled a hole in the middle, making sure it was big enough to go around the area to retain but not too big to slip past the small flange that would hold it in place.  I cleaned up the drilled hole with an exacto knife and then trimmed the edges to size it down and make it closer to a rounded shape.  I then cut a small opening in one side to make the piece function like a clip that would flex and slip over into place but stay secured in place once there.  After that, I sized it up and it was too thick so I rubbed the piece on sand paper until thin enough and finally had my retaining clip.

(In the first picture, the piece with the orange disk around it is connected to a wire and needs to go through the hole at the bottom of the image in the bracket, then be retained once in place.  The bracket is flipped 180 on the other 2 pictures.)

How did I come up with this?  I do not know.  I'm hoping that these creative solutions keep coming though!

After fixing the horn, I then reassembled the switch unit and the button worked phenomenally.

Since the switch was fixed, it was time to tackle the wiring.  The first thing I did was retrieve the wiring diagram for the RC51 from online.

2004 RC51 (VTR1000F) Wiring Diagram

1975 CB750F Rewired to Mate with RC51 Switch

I cut the connectors off and meticulously matched up wires from the new diagram to the old diagram (if only the 1975 version was in color).  About 70% of the wires matched up directly but there were definitely some discrepancies.  I replaced all wire ends on the bike and the new switch with fresh connectors to be mated up.  I then connected the wires that were a given (that 70%).  After that, I spent a lot of time validating what wire served what function and how to mate it up.  There were a couple of color mismatches and some colors that one or the other didn't have so I had to nail it all down by staring back and forth between the two wiring schemes.  Eventually I got it sorted with a few wires to spare on either side.  I had to do some specialty wiring for the horn because the circuit in the new switch didn't function like the old switch (extra wires in the new switch).  In the end it all go sorted and, although seemingly messy to the eye, I got a fully functional new switch properly wired and installed and new lever put on (I also put shiny new bars on).

RC51 Switch on 1975 CB750F

My electrical issues were resolved so I finally replaced all of the fuses with new ones.

1975 CB750F Cleaned Up Fuse Panel

Ready to fire?

Somewhere in all this I had tested the 4 cylinders for spark and it was good across the board so that was a relief.  I had also tested the starter and it turned over just fine.  I now had the electrical mostly sorted, and the tank was coated, dry, and ready to be installed so it seemed like I was ready to try and start the bike.

I hooked up the tank, started to fill it with fuel, and it seemed good so I switched the petcock to run/on to fill the float bowls.  After a few seconds I had 2 leaks: one on the #3 carburetor float bowl drain plug and one at the petcock.  I drained all the fuel out of the tank and all of the float bowls.  I then disassembled the petcock to see what the issues was.  It appears that I needed a new rubber fuel filter seal, not in the petcock, and a new float bowl drain seal.  

I will need to order the parts and can't try to fire until I get the leaks fixed.  Time to wait.

In addition, the bike is stuck in 1st gear and I'm not sure why.  This may be an issue with a shift fork in the transmission which, if that is the case, will mean that I have to take the engine out and go through it much sooner that I would have liked to.  Being that it's on a center stand, I can still fire it up and I'm hoping that if I get the rear wheel spinning that I can pop it out of first but only time will tell.

Carbs and Tank Electrolysis Continued

When I last left off, the tank was undergoing electrolysis and the carburetors had just been disassembled.  Let's talk about the tank first.

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)

Motorcycle Trickle Charger

would go to "Charged" after about 30-60 seconds which means that the process wasn't functioning.  I tried adjusting my setup, unplugging, plugging back in, adjusting again... still no success.  Eventually I dropped the voltage from 12V to 6V and this seemed to let the process work.  Over time, however, the charger would read charged again.  My guess is that the 1.5 amps may be too weak but I really didn't want to buy a new charger just for this process since I figured I wouldn't need to do it that often.

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)

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.  

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.

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.

Proper Ultrasonic Cleaner

 As you can see by the top picture, the whole carburetor fits in there so I could basically run one carb and all of its components in a run.

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:

1975 CB750F Cleaned Carb

Before:

After:

1975 CB750F Carbs Cleaned (From Air Box)

1975 CB750F Carbs Cleaned (From Air Box)

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.

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.

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.

MEK (MethylEthylKetone)

To rectify the situation, I resorted to aggressive measures.  The most aggressive solvent that was recommended by Red-Kote was MEK (MethylEthylKetone) so that's what I decided to get.  This stuff was not easy to find.  I finally found it at a plastics shop.  

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!!!