"Poor Kid" 1981 CB750K - first build

Brief update:

I ordered a manual petcock and a starter relay, I'm tired of waiting. I'm gonna bypass the petcock vacuum line just like everyone told me. A little grumpy about it but I want to ride my bike, and I can swap it back to the old way just as easily. Waiting on delivery, hoping before Friday.

Also a friend in Dallas (PO actually) tipped me off about a CX500 for sale. Might see some shots of it in the background soon...

1981 CB750K (impatient to ride)
 
Starter relay reinstalled, and a disappointed face: the petcock was of course, incorrect. It is a petcock specifically for an 81 750K but of course, my tank probably isn't. It could be a tank from an 80, a 79 even.

So naturally I'm kinda pissed but it's what I get for ordering Chinese OE style parts. Shipping it back would cost as much as the refund. Fck it- I just typed in exactly what I needed on eBay.

3/8 NPT female petcock

And now I'm waiting for just that, another universal part. This is the last time I'm messing with this part, especially since I was somewhat goaded or coerced into the plan of vacuum petcock abortion.

So the tank gathers rust yet again and will need to be cleaned before new petcock goes in... AGAIN. Come on now. It's only a matter of days.

But something else is in the works. I've been alerted to the presence of an 81 CX500C in great shape, for a pittance. I've been trying to set the deal up with the owner. He's a retiree in no rush. But there may be another identical year bike in the garage this week... Stay tuned. Gotta keep the ol chin up for a few more days.
 
slather the inside of the tank with oil, it'll keep the rust from forming
 
Wow man, great job attacking this thing especially as a first timer. All your efforts will be rewarded when you get to ride. Keep it up.
 
Cool build so far. Advice on rust proofing. You have to fill the tank with fuel to the top completely with no air pockets. if you leave air, even with oil you can get rust, no air = no rust. Its called oxidation for a reason. good luck, you may need to line it will POR 15 to stop it completely, but if you make sure anytime it may sit that you fill it to the top with the petcock closed and stabilized gas it should be ok.

Cheers.
 
Thanks for the props and the advice. I know why it's rusting, i'm just not able to prevent it so well... last time I sealed it up and let it sit completely full of gas and Sta-bil (anti-rust/corrosion) and it still caught some rust. If only bikes had floating ceilings like car tanks...

The NEW new petcock is supposed to be here on Friday. I got some chain and acetone and I'm just gonna put the chain and acetone in there, shake it like a Polaroid until the big surface shit's out, then trust the inline fuel filter. I should have resealed it but I elected to take the easy way out. So, Friday is the NEW last part day.

There is some great news. I'm picking up another bike tomorrow for certain. A clean titled 1981 CX500C... and when I get it, I'll have two 81 Hondas in the garage. People are telling me not to buy another before the first is finished, but if you knew how cheap it was you'd get it too.
 
Re: Re: "Poor Kid" 1981 CB750K - first build

kraptastic k said:
People are telling me not to buy another before the first is finished, but if you knew how cheap it was you'd get it too.

Those people can walk around their garages and aren't to be trusted.

Might want to check to see if you're due for a tetanus booster
 
Yeah this bike has lost all its rust... No good anymore. I know the CX needs an igniter which means it's not running, so that's a start?


1981 CB750K
tentative 1981 CX500C
 
kraptastic k said:
There is some great news. I'm picking up another bike tomorrow for certain. A clean titled 1981 CX500C... and when I get it, I'll have two 81 Hondas in the garage. People are telling me not to buy another before the first is finished, but if you knew how cheap it was you'd get it too.


HA......wish I'd heard that one a few bikes ago....
 
Good get, always good to have one waiting for when the first is finished ;D the CX's are easy to work on, valves are a breeze, carbs come out super fast etc. You started with the harder bike having 4 of everything, the CX is half the work LOL.
 
I've heard the CX will be ultra reliable and it will be a favorable commute bike, in comparison to the highway-sprint style of my CB. I sure wish I knew! Either way, I'm sitting in my living room, waiting to go get it. Two isn't too many.
 
Uh oh... Look what I found.

1981 CB750K
And
1981 CX500C
 

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Now that is a great starting point on a CX. I wish mine was half as clean as that at the get go. Good luck to you on it. Any directions you are going to go with it after the CB?
 
Thanks! Everybody sees the crazy good deals on bikes... Thought my turn would never come, but now I have a solid platform for build #2.

Yes, I'm very excited to build another purpose driven bike. Since the CB is my highway sprint bike/tuner, I would like to make a reliable commuter bike that can hop curbs and dodge down shoulders. Probably some MX bars and very few other mods.

I'll post a link to the build thread and tell the story better.

1981 CB750K (getting there now)
 
Heck yeah man, exactly what I'm building my cx for. A solid runner for around town, backroads, but still able to do a 300 mile trip to college without worry
 
McBrenner, that's spot on. Something that I won't be frustrated on in traffic. Or something that gets me out of said traffic.

No, I don't think this bike was listed... Snagged it from a shop in Corinth, TX. Bitch of a drive

1981 CB750K (getting there now)
 
I ordered two bunk ass petcocks and I'm thoroughly disappointed with both of them not fitting.

Some haphazard fabrication also ended up with the worst brake light I've ever seen. It will have to do for now.

Brass pipe fittings and a bit of improv have left me with a true rat setup. The new starter relay is also bunk I think- I had to jump it with a screwdriver.

The idle is extremely high now with consistent fuel flow. Backfiring occurring every 15 sec, but I won't let it run like that for intervals of more than 8 sec. Cyl #1 & 4 seem normal. 3 is cold and 2 is very very hot, assumed lean. Adjustment of the idle mixture screw did not appear to help.

Theories: vacuum leak at the boot. Can a bad seal at the exhaust header cause a lean or high idle condition?

Pilot fuel system could have clogged in carb 4, aka cyl 2?

No spark at cyl 3?

The issue with fuel spilling from the air filters is eliminated. No problems exist beside the faulty starter, the still-leaking case cover, and the above conditions.

Please advise.

1981 CB750K (headscratcher)
1981 CX500C (back burner)
 

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