"Poor Kid" 1981 CB750K - first build

^+1

Pop the service manual out and run through it. It'll walk you through, start to finish.
 
Okay everyone. The bike, which was at a friends house, is now home and I'm working on it today. Before I do any repairs, I need to send the poor starter motor out to pasture. Little guy spins out more than 60% of the time, likely due to my first and POs last poor starts. Rich, you once said you had a starter motor... Well, I'm looking for one. PM me some prices gents?

1981 CB750K
 
Also I dropped this thing while pushing it home one shitty day. I'm pretty certain I bent or damaged the front rotor because it will hum while pushing it slightly... Coming from the rotor. are there common sense solutions like having it turned on a lathe or am I about to look for a new rotors?

And yes, it will be plural, because I likely just do a new wheel, brakes and forks.

1981 CB750K
 
I no longer have any starters; sorry man.

You can lay your brake rotor on a sheet of glass to see if it's warped. Must've been quite a drop!
 
you know, it wasn't quite a drop. I don't honestly think it could have damaged the rotor. maybe the pads are just rubbing for no reason, eh? I'd be happy to try out the non-replacement fixes anyone can dream up. Otherwise I might be trading a firstborn...
 
There's always a reason. Get the front wheel off the ground and look at it.
 
humming can be caused by a dragging caliper

or a plugged up return hole in the master cylinder holding the brake partly on

as rich ard says get it off the ground see how it spins

if the brake is dragging open the bleeder if fluid comes out and the brake frees up then you have a master cylinder issue

if nothing comes out whack the caliper with a rubber mallet if the brake frees up clean the caliper piston and the caliper

sliders lubricate the sliders and reassemble
 
Agreed, a warped or bent rotor would most likely cause a pulsation, not a hum. Sounds like the caliper isn't free to move on the slides and got pushed against the rotor in the drop so now it is dragging... just as cxman described.
 
Bike reassembled and running after all the little boo boos. Kinda poppy and backfirey when it's cold, but well enough. My starter is dead, or near it- gotta find one soon.

That brake is still dragging. I malleted it and tried to free it but I couldn't figure out what was bound. Maybe a stuck piston? It did fall from ground weeks ago and was mostly unattended. I know this can be fixed with common sense.

I did some custom work with the dremel, and made some changes to my fuel lines. These are challenging to run with the pod filters, but my new system will prime and feed both lines from kickstand or while running, while incorporating a fuel filter. About damn time!
 

Attachments

  • uploadfromtaptalk1389139328228.jpg
    uploadfromtaptalk1389139328228.jpg
    93.9 KB · Views: 858
  • uploadfromtaptalk1389139342533.jpg
    uploadfromtaptalk1389139342533.jpg
    91.3 KB · Views: 848
That's the spirit! Never half ass or mess around with brakes. Do it right and do it proper. Only thing worse then them not working is them suddenly working.
 
Could have tweaked your forks a little in the triples. I dumped my buddy's Sportster at low speed and while it looked like they had been bent, all we had to do was loosen the triples and realign everything.
 
got it all fixed up, i thought, just reassembled the bastard and flushed fluid, then bled it. it was a little spongy still but i took it for a ride and died out for fuel starvation. it's been a constant battle to keep these carbs fed, but a little bit more modding should have it just fine. I primed it up and rode home without incident, noting a significant decrease in the bike's pull at 1/4 throttle in comparison to 1/8.

I'm ordering my valve adjustment tool and a new starter from a forum member, so i can't do a final tune just yet;

is it safe to lean out the mids by adjusting needle clips, specifically leaner? maybe i can get a little more power from that range of the throttle without changing mains and all.

also, i really got to clean up some of the wiring behind the headlight bucket, where the new OE harness i ran was dangling wildly. somehow this caused me to lose the functionality of my headlight and light controls, so i have to unwrap it all. living the dream!

what's your trick for finding that wiring bug?

and really, too windy to ride in town today. waiting on a starter for the CB, and a CDI for that CX500 i bought. it may start finally after 6 years.
 
squeeze the brake lever and tape or zip tie it to the handle bar over night

it will allow any air stuck to the sides of the line to rise out of the line and caliper and get rid

of the spongy feel it will firm it right up
 
Will do.

Got a bit distracted today. The leak of brake fluid destroyed the electrical switch beneath the master cyl. Also, my headlight still doesn't work. I had only taped up a few components, now it and the control don't work. Weird! The bike still runs and all just no headlight or light control indicator.

I think the carbs are totally set up now... See attached
 

Attachments

  • uploadfromtaptalk1389572834950.jpg
    uploadfromtaptalk1389572834950.jpg
    113.2 KB · Views: 927
Might it be that you've got a weak or bad ground somewhere? Seems odd the brake switch and the headlight would go out at the same time from separate issues....
 
I'm thinking it must be a ground on one of three or so wires. I'm pretty bad with the multimeter and it shows. I feel like I will end up clipping all the controls after looking at the piss-poor solder job I did. Such a little gremlin! I was just about to take it to work and do some fab, but now I have to worry about wires.

Also, I meant that the fuel lines are set up; the carbs have a way to go.
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light
    • www.jadusmotorcycleparts.com
    www.lostapostle.ca/
    www.sparckmoto.com

    Spread the Love

    Back
    Top Bottom