Topic: CB750 K1 Resurrection

[ZTatZAU]

Hey, Thank you David!  Thanks Stu!

I've used electrolysis in the past to remove rust from small parts before... with a setup like this...



... but hadn't yet considered it for removing rust from my gas tank.  However, your well-reasoned suggestions and advice are well taken!

...Electrolysis works well too if you have a battery charger that can run manual mode and don't mind cleaning the rebar or other sacrificial steel anode often...

By "manual mode", do you mean a constant voltage or constant current mode?  How about the old Sears Battery Charger you see in the background of the picture above?  This charger has 2, 10, and 50 Amp settings, would this charger suffice?  And at what setting?  And do you recommend hooking up the tank and electrode directly to the battery charger?  Or to a 12 Volt battery, that is being replenished by the battery charger?

I agree with David about doing electrolysis. I use washing soda 1/2 cup to 5 gallons water and an electrode made from 5/16" all thread bar nutted w/fender washers to a cut down paint can cap.  Positive lead to electrode, negative to the tank at the hump rubber mount flange (sand off paint to expose fresh steel for connectivity)... Edit... The paint cap insulates the positive from the tank so the electrode draws off the rust from the tank and attracts the rust to the electrode.

I understand that the electrode must not touch the metal tank, but I can't see any insulation at the end of your threaded rod to prevent contact.  Are you relying solely on the rod being securely fixed to the plastic paint cap to avoid any contact inside the tank?

It'll take me a while to put together a sealing plate/gasket for the petcock opening and then create a suitable cap and anode. I'll let you know how it goes.

Thanks again for your replies!  ZT

[newday777]

Yes the threaded rod is solidly fixed to the cap with a nut and a fender washer under the cap and another on the outside to lock them solid.
I use an old but still good battery and a 3 amp charger hooked to the battery and a small jumper cable to the tank and anode.

[ZTatZAU]

Thanks Stu!  I'm on it.
ZT

[ZTatZAU]

David & Stu,

Thanks again for the info you provided!  I'm just about ready to proceed with the electrolysis with the setup shown below...



... But before I begin, I have a couple of follow-up questions:

1)  I was concerned about the large clump of rust in Stu's first picture, at the very top of his anode... just under the cap.  I could imagine that clump getting large enough to make contact with the bottom of the filler neck and shorting out the setup.  It may not be apparent in my second photo, but to be on the safe side, I installed a tight-fitting rubber hose at the top of my anode under the cap, that extends about 1/4" below the top of the tank to help prevent any rust build up from contacting the filler neck?  Do you see this rubber hose insulation as necessary, a good idea, or perhaps causing any problem with the process?

2)  I last flushed my tank with a two-stroke mix of gas and oil to avoid any additional or flash rusting.  The gas has now all but evaporated but do you see any need to remove the thin coating of remaining oil from the interior of the tank, (with solvent), before proceeding with the electrolysis?  That is, might the remaining thin film of oil inhibit the electrolysis process in any way?

3)  When using electrolysis in the past to remove rust from small parts, the finished parts are often discolored with a dark, almost black, color.  Can I expect the same dark discoloration will happen to the tank's interior once the electrolysis process is complete?

4)  When the electrolysis process is complete, is the new (hopefully) rust free surface subject to the same flash rusting as would be the case with Evapo-Rust or other acidic chemicals?

5)  My plastic spray can cap is very tight fitting around my filler neck.  Should I add a few small vent holes to the top of the plastic cap to prevent any build-up of hydrogen gas?

Yeah!  I do tend to "over-thinking" such things; but will appreciate your patience and assistance!
ZT

[RAFster122s]

Not sure if the oil will cause an issue...time will answer the question for certain. I don't think your hose will be an issue, not needed if cap fits securely. Hydrogen gas shouldn't be a huge issue, but if concerned drill a couple 1/4 inch holes for it to escape. Just don't stick a match in the tank after popping the cap. So you aren't capturing the hydrogen to make yourself a hindenberg balloon?

[ZTatZAU]

Thanks David!

When the electrolysis process is complete, have you found the interior of the tank to become a dark color?

And do treat the tank interior in any way, when the electrolysis is completed?

ZT

[RAFster122s]

Rusty metal gets replaced with whatever you are using as an anode material, so the color depends a bit on that material. It won't match the rest of the interior of course.
After electrolysis just a good rinse of denatured alcohol, throw some 2stroke oil in to coat the interior and then put it back in service.

[ZTatZAU]

Rusty metal gets replaced with whatever you are using as an anode material, so the color depends a bit on that material....

Interesting!  I didn't realize that was the case; but I can see where an old rebar anode might turn a piece darker than a bright metal all thread anode rod.  I suppose time will reveal that answer as well.

After electrolysis just a good rinse of denatured alcohol, throw some 2stroke oil in to coat the interior and then put it back in service.

Seems reasonable!  Essentially the same treatment following any other rust removal process.

I appreciate the info you've provided, David!
ZT

[BenelliSEI]

I have yet to try this method. Once again, someone else’s project inspires! Please post photos of the outcome. I have a really nice K1 tank that needs a bit of cleanup. Will try this, for sure. Thanks!

[ZTatZAU]

I have yet to try this method. Once again, someone else’s project inspires! Please post photos of the outcome. I have a really nice K1 tank that needs a bit of cleanup. Will try this, for sure. Thanks!

Will do BenelliSEI, but it may be a few days before I can get back to this.
Stay tuned!
ZT

[MauiK3]

I've used anodes made from plain mechanics wire or rebar tie wire on a tank. I twisted the wire into a shape I could suspend into the tank without touching it. It was a slow process but it worked

[ZTatZAU]

I've used anodes made from plain mechanics wire or rebar tie wire on a tank. I twisted the wire into a shape I could suspend into the tank without touching it. It was a slow process but it worked

Thanks for your reply MauiK3!

I had enough extra time this morning to get the electrolysis process started before heading out for other planned activities.  I'll check on the progress later this afternoon to see how it's going.



Stay tuned for updates on progress.  ZT

[ZTatZAU]

ELECTROLYSIS FOLLOW UP
As previously mentioned, the interior of my gas tank only appeared to have some light surface rust.  Nonetheless, I did one 6 hour electrolysis session yesterday during which a substantial amount of rust was collected on the anode.



I then did another 12 hour session overnight, with the anode oriented toward the other side of the tank.  This second session deposited about half the amount of rust on the anode, than what was collected on the first session.



 I then did another 4 hour session this morning with very little rust accumulation on the anode.



I then dumped the dirty washing soda electrolyte mix (I used 1 cup/5.5 gal.) and flushed the tank well, with water.  After dumping out the water flush, I used a heat gun to dry up the interior of the tank best I could.  Then a one quart flush with 91% IPA to, hopefully, remove any remaining moisture, followed by another quart flush of two-stroke gas/oil mix.  I sloshed that around pretty well and drained out the two-stroke mix, so the remaining gas would evaporate to leave a light oil film on the interior of the tank.

Sorry BenelliSEI, but I tried to take some "after pix" for you, but my iPad camera didn't do so well on that; though I can tell you that it does look pretty nice in there now, with no evidence of flash rusting.

My thanks to everyone who offered their advice on using electrolysis!  Moving on...

GAS CAP QUESTIONS

I'm still waiting for my petcock rebuild kit, so I got to cleaning up my gas cap and its innards.  Upon re=assembly, I'm somewhat confused about the large rubber double lipped gasket.  Unfortunately, the FSM and FPM weren't much help; and the diagram on page E-14 and 14 didn't even fully identify all the parts or their item numbers.  So, I've added my own part numbers, in the image below, for clarification ...



If I'm not mistaken, I've arranged the components, from left to right, in the order in which the parts are supposed to be "stacked", when assembled.  Please correct me if I am mistaken on any this!

My question has to do with the large double lipped rubber gasket.  How many of the components (numbered 3 through 6 in the photo above) are supposed to be "enclosed between" the two rubber lips of the large rubber gasket (number 7)

That is, do I stack all the components (# 3 through #6) together, and stretch the (#7) gasket lips around all these components?  Or does the (#7) rubber gasket lips only go around the large flat washer (#5) and the bottom cap (#6)?

Thanks in advance for any guidance on this!
ZT

[ZTatZAU]

RE: My GAS CAP QUESTIONS



If I'm not mistaken, I've arranged the components, from left to right, in the order in which the parts are supposed to be "stacked", when assembled.  Please correct me if I am mistaken on any this!

Well, apparently, I was mistaken on the stacking order of the components.  While the parts manual diagram didn't identify all the components with item numbers, the diagram did key me into the correct stacking order.

Turns out, (with the cap inverted on the bench), the large flat washer (#5 in my photo) goes under the dished washer (#3) rather than under the bottom cap (#6) in my photo.

Then once the components are stacked in the correct order, the large double lipped rubber gasket (#7) is stretched over all these components (#3 though #6).

My cap is now back together correctly (I think?) as it appears to open, close, and seal nicely on my rust free gas tank.

FWIW!  ZT

[BenelliSEI]

Nice work. Amazing what came out. I’ll definitely follow your steps on my spare K1 tank. Thanks for all the details (everyone)!

[ZTatZAU]

Nice work. Amazing what came out. I’ll definitely follow your steps on my spare K1 tank. Thanks for all the details (everyone)!

Thank you kindly, BenelliSEI.

I'm sure I'll continue to need a lot of help with my K1's resurrection so I'm happy to help others when I can.

ZT

[HondaMan]

I have yet to try this method. Once again, someone else’s project inspires! Please post photos of the outcome. I have a really nice K1 tank that needs a bit of cleanup. Will try this, for sure. Thanks!

Me, too!
And a K3, and a K4...

[ZTatZAU]

I have yet to try this method. Once again, someone else’s project inspires! Please post photos of the outcome. I have a really nice K1 tank that needs a bit of cleanup. Will try this, for sure. Thanks!

Me, too!
And a K3, and a K4...

Again, it's nice to know that my fumbling and bumbling along here have inspired others to try something new!
ZT

[ZTatZAU]

My next (silly?) question as I continue to feel my way along with my K1's resurrection.

I'm quite sure that the two little tabs on my petcock screen were facing down towards the bowl when I took my petcock apart as shown in my first pic.  I assumed the tabs are designed to facilitate removal of the screen for servicing... Though the tabs on my screen didn't really help in that regard, and I tore a hole in the brittle, fifty year old screen.



Now, as I'm putting the petcock back together, I'm wondering if the two little tabs are supposed to face up to capture the raised center fuel passage-way, that I've marked with the yellow dot in my second pic.

I've also noticed that my new screen is slightly convex on the side with the tabs, which may play into the proper orientation and positioning of the screen.

Any guidance on this is appreciated!
ZT

[BenelliSEI]

I always install them “down”. They are fairly useless as pull tabs, but I think that’s their purpose. I can’t see any reason for orientation.

P.S. I didn’t think anyone else still used 35mm film canisters for small parts! Not so easy to come by anymore……

[ZTatZAU]

I always install them “down”. They are fairly useless as pull tabs, but I think that’s their purpose. I can’t see any reason for orientation.

P.S. I didn’t think anyone else still used 35mm film canisters for small parts! Not so easy to come by anymore……

Thanks BenelliSEI!  I'll install the new screen with the tabs facing down.

As for the 35mm film cans, I've stored all manner of things in them over the years, (some of which I shouldn't mention here  ), and I still have a pretty good collection of them.  That can actually contains my lifetime supply of "Seal Lube" which is what I wound up using on my fuel connector tee o-rings.   I'm using a little more of it now to lube the petcock's fuel lever, spring, and o-rings.

ZT

[newday777]

John
I still have a few of the canisters and use them for tiny machine screws, nuts and washers.

[BenelliSEI]

John
I still have a few of the canisters and use them for tiny machine screws, nuts and washers.

Me too. Each of my bikes has one on board for #1157 stop/tail light bulb, just fits!

[newday777]

John
I still have a few of the canisters and use them for tiny machine screws, nuts and washers.

Me too. Each of my bikes has one on board for #1157 stop/tail light buld, just fits!

Cool!

[ZTatZAU]

IT'S ALIVE... AGAIN!

After rebuilding my K1's carbs & petcock, servicing my rusty gas tank, and putting it all back together with all new OEM rubber components, I fired it up for the first time in 11 years.  I was happy to have it running again but not so happy with how it was runnng.  Seemed somewhat rough and weak at low RPMs and could hardly make it idle; though it smoothed out and sounded pretty good at 2000 RPMs and above.

So, I set the valve tappet clearances (they were a bit tight), and set the point gaps at 0.014" (they were a little tight too) which seemed to help the idling some; but then set about testing the ignition timing.  This is where the plot thickens and my next round of questions begin.  Hoping again for some help from the more knowledgeable CB750 folks here!

First, I'm wondering what to make of the timing marks on my 1971 K1 (mfg 12/1970)... which look like this...



whereas the timing marks in the Honda Shop Manual look like this...



which are the same as the timing marks in my OEM 1971 Owners manual which look like this...



I'm thinking I must have replaced the breaker point at some time in the past, though I can't recall doing so.  I did at one time loan the bike to a brother-in-law who may have changed the points and breaker plate which has a date (?) code 2.10.07 and markings that looks like TEC.  Perhaps this might ring a bell with someone who can tell me what I have.  But the breaker plate is separate from the rotating advance mechanism that has the timing marks engraved.

While the timing marks shown in the OM and SM look like this... T I I F  1-4

The timing marks on my advance mechanism look like this... T I  F I  1-4

I'm not so concerned with the difference in labeling, but rather the difference in the spacing between the T & F index marks.  Can anyone tell me what's going on here and what I have in there that may not be correct?

In any case, my next question has to do with checking/setting the ignition timing.  I do have a strobe light but don't have an adapter that will allow me to attach the strobe light to the #1 high tension lead and spark plug.  So I was going to set the timing with the continuity setting on my multi-meter.  Unfortunately, when I rotated the crank past the 1-4 F index mark,,, even though the points opened, I still had a solid continuity tone from my MM with the points open.  This was my setup...



Please let me know if this method should work as I thought it should?  Is it possible that that insulating fiber washers at each point connection is faulty and that's the path that provides the continuity when there should not be continuity with the points open?  Or could the continuity be the result of the condensers in the circuit?

I'm scratching my head on this one and hoping for some suggestions and advice.

PS:  I sycn'd the carbs best I could on the bench before installing them and they all looked the same, and opened and closed together the same amount but I haven't yest attached any vacuum gauges to the carbs as my buddy with the gauges can't seem to find them at the moment.  Nonetheless, I'd like to be sure the ignition timing is correct before attaching the vacuum gauges.

I do appreciate the help!  ZT