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Author Topic: "Poor Kid" 1981 CB750K - first build  (Read 26694 times)

Offline kraptastic k

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #10 on: May 02, 2013, 23:50:39 »
Some more chatting with Eric at Swifty's and a bit of ingenuity have resulted in filtration installation. A bit more soldering tomorrow... Only right hand bar control and reg rec install remain before tuning and riding.


Notice I had to grind/bend the tabs that used to hold side covers. I'll compromise, this is a mock tank and form must follow function.


1981 CB750K (getting there now)


Offline kraptastic k

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #11 on: May 16, 2013, 03:38:56 »
I decided that this whole brake caliper nonsense had to end. I put the old piston back in. the piston won't be pushed out to the pitted area until the new pads wear down, giving me some time to ride and consider upgrade options.

Still confused on the reg rec- we think we have it figured out, but I still feel wary about some of the wire color choices and pin sequences. If the battery dies, I guess I'll know. Spark wires and coils are soldered and run as well. I couldn't figure out how to run my own kill switch, so I nabbed one from Rich Ard.

Discovered a nice oil leak out of the left crank cover. Looks like it was dropped once or twice. If anyone has a good one of these I'll buy it off them - just a PM and a price for anyone reading.

To my horror, the tank I de-rusted and stored with fuel and Sta-Bil (cause of red coloring in fuel) is of course rusted again. Dull brown rust on the bottom, no shiny metal on the inside.
Damn, that is irritating. I mean... Really irritating.

I could be riding on Friday, had I not trusted one of the billions of half assed rust removal quick fixes.

What the hell do I need to do to kill and stop the return of this rust? It's time to ride!

...anybody?




Offline kraptastic k

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #12 on: May 16, 2013, 16:02:06 »
Hmm. Vinegar and mineral spirits, another one from the forums. I have all that stuff as it is. I'll try it I guess. Will post results as I bite my fingernails and stare at the mailbox waiting for my switch. Oh, and payday is tomorrow. It's like two Christmas' occurring simultaneously.

1981 CB750K (anxiety destroyer)


Offline Rich Ard

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #13 on: May 16, 2013, 16:19:29 »
Vinegar does the trick - then, afterwards, rinse with a baking soda solution to neutralize the acid, and then coat liberally with oil (I use Marvel Mystery Oil, because it's fun - some people use WD-40 or two-stroke oil or whatever's handy).

Your switch oughta be there tomorrow - best luck man!
unplug the connectors from the harness and multimeter the shit out of them

Bad Points, a comic :: CB450 Restomod (sold) :: Viragostrosity :: GL1000 daily rider :: Kaw 175

Offline kraptastic k

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #14 on: May 16, 2013, 16:27:30 »
I know man. I'm still impatient.


Will the added oil disturb my carbs or the running of the bike? I plan on running it shortly after de-rusting.

1981 CB750K ()


Offline Rich Ard

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #15 on: May 16, 2013, 16:30:31 »
Don't pour a whole gallon in there or anything, just enough to coat the thing. :)
unplug the connectors from the harness and multimeter the shit out of them

Bad Points, a comic :: CB450 Restomod (sold) :: Viragostrosity :: GL1000 daily rider :: Kaw 175

Offline kraptastic k

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #16 on: May 16, 2013, 16:38:46 »
I really want to make sure this thing is well coated. Can't I just put fuel in it directly after, if I use the mineral spirits to dry it out? Of course it just rained in TX so I may be forced to wait for humidity to decrease.

1981 CB750K (getting there now)


Offline Rich Ard

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #17 on: May 16, 2013, 16:39:53 »
Most likely, yes.
unplug the connectors from the harness and multimeter the shit out of them

Bad Points, a comic :: CB450 Restomod (sold) :: Viragostrosity :: GL1000 daily rider :: Kaw 175

Offline kraptastic k

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #18 on: May 18, 2013, 02:40:14 »
I went into the garage with low hopes today. Got back from the hardware store and grabbed my switch out of the mail.

I wired the switch and mounted it. All the headlight functions are present and the on/kill and starter features all worked. Everything seemed cool. Secured almost everything in the wiring.

I hooked up my tank to a car fuel filter and ran fuel to the carbs. Oops! The 'On' position causes fuel to leak out from under the petcock. 'Res' seemed to work, and fuel flowed into the carbs. But then I realized that fuel was overflowing... Not from the vent tubes. But from the air filters. No throttle- just fuel through the line into the cleanest and driest carbs you ever saw. I think it may have been the petcock, as the GSXR carbs have a vacuum line that runs to their petcock, and the Honda petcock lacks a second port. Well... I had to kill the tank rust anyway so I'll have to find a suitable petcock at the same time.

I removed the tank and just held a long piece of line up to feed fuel into the engine. With everything plugged in, I tried to start the bike twice. Saw some blue smoke out of the 3rd cylinder where the header pipe meets the block. Was told to check "split keepers?" I'm not really sure, but I'll check tomorrow. Below is the kit I received and I may have installed the little flanged pieces in the lower middle of the pic.

My seven wire SOHC reg rec got very hot initially (enough to make a smell of burnt plastic) perhaps because I used it on a DOHC... I am determined to make it work and will have to run tests with the ohm meter...

Set the front brake up as well, but we had trouble with air in the lines and decided to leave it overnight to gravity bleed.

Itching to just hear an idle now.



1981 CB750K (working out kinks)


Offline kraptastic k

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Re: "Poor Kid" 1981 CB750K - first build
« Reply #19 on: May 18, 2013, 14:29:07 »
Goood morning.

My buddy dropped by and wanted to see some progress, so I went through the steps of setting up the tank and fuel filter again to try and start it. Plugged everything up with a big car fuel filter and ran some fuel in, pulled on the choke and hit the starter.

I was surprised by a strong, loud idle  after the first press, no exhaust leak, and when I reached back to touch the reg/rec, it was still room temperature. I killed it before the fuel ran out of the line and stepped back, blown away.

I can't believe I got those swapped carbs to work so well on my second ignition attempt.

Of course I'll be messing a little with the carbs soon, but this is the list for the next few weeks:

New petcock with an 8mm vacuum hose barb or fitting on it.

Continue bleeding front brake: lever feels soft and bike will not stop when lever depressed. (Cheer up lever)

Put vinegar in the gas tank for two days and annihilate rust, follow with baking soda/ water, then dry with spirits, grind side cover tabs off tank and fill with fuel/replace onto frame...

Ride?



I don't even have a helmet!



1981 CB750K (on the homestretch)