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1976 CB750 K6 Build

yooper

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Hey all,

This thread is going to show my project from start to finish.

Bought a 1976 CB750 k6 for 400$. Kinda a weird deal but if it goes bad i can part it out and make most back.

The guy i bought it from never touched it, just bought it from someone, put it in his garage for a year, then sold it to me. The bike was posted as a 1972 but the VIN on engine and frame show its a 76. He claims the engine was gone through by the past owner (if its not, no big deal i like working on engines) so i might not have to break into that for a bit. When I bought it I couldn't get any spark so I couldn't test if it was running or not, but the bike seemed to be in decent shape, has new tires, new carb boots and the previous owner defiantly did some custom work.so I bought it.

My plans for the bike as of now:
Paint the frame black
Paint the rest of the wheels black
Paint tank Black and tan
Make or buy a brat style leather seat that can hold two
Make a cafe style seat (for single riding)
relocate oil tank below carbs (gonna fab a new tank)
Find a new spot for an anti-gravity battery (most likely on the bottom of the bike like czeromedia did)
sort out wiring harness, remove blinker and electric start components
remove electric starter.

Link brings you to photos of the bike.
https://goo.gl/photos/Q46191PrPZTQ8CM58

Ill post pics after every time I put some work in.
 
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First Day of Work

I figured I'd start with the part I dread the most... wiring.

Took off handlebars, light, RPM meter, and custom battery box in order to free up wires and take off the wiring harness.
So I already hate the guy who put work into this bike. All the wires have been triple wrapped in electrical tape so that was fun.

Found a few reasons I might not be getting spark, but a deeper look at the wiring diagram will determine that for sure.

Few pics from today- https://goo.gl/photos/An9EwhBPgEZBgQAHA
 
I wouldnt remove the starter....these motors are not designed to use kickstart only, they are a backup for the starter motor. The kickstart mechanism inside can break with abuse and you can bend the kickstart shaft if you really jump on it. The shaft only rides on aluminum in the side cover, I've seen a side cover wear oblong from long term use. Electric start was still not considered 100% reliable when the bikes came out, they always liked a backup system...the kickstarter. Keep in mind anything that goes wrong or breaks in the kickstarter meens you have to split the cases to get to it. You will get really tired of kicking if you ever have issues with it wanting to start or if it floods or run it out of fuel.

Be careful with the oil tank design, if not done right on the return side the tank will drain back down into the engine when you shut it off they you will have a dry start when you go to start it back up. Also make sure you stay at the same capacity, everyone wants to hide there oil tank or make it tiny....oil helps cool the engine,if you reduce the capacity you will make it run hotter. Oil tanks are something I dont recommend messing with, If you want a bike without an oil tank I suggest looking elsewhere or later model dohc bike. Many people think well its just two lines going to a tank, but keep track of which one is which if you build a tank, wrong line in the wrong spot will destroy your engine. Also keep in mind to properly vent the tank and realize that it serves as an air/oil separator, lot of people run into issues with blowing oil out of the tank vent of aftermarket tanks because they have no air/oil separator in them.
 
Thanks for the advise dirtdigger! This forum is already proving to be helpful.

Looks like I'll be leaving the starter in the bike.
 
No problem, Its pretty easy to hide one wire and a small starter solenoid and still have the convenience of a starter. You can still kick it once in a while if you want to, dont really know why people want to kick start their bikes all the time, all it takes is one kick back when the motors hot and you will wish you had the magic button.
 
Got the wiring harness out. Decided I'm just going to make a new one. In the process of making a schematic for it at the moment. Ordering a new rectifier/regulator from ricksmotorsportelectrics. and a new starter solenoid. I'll post my new wiring diagram when its done.

While I was taking the plate that guards the chain off one of the screws stripped. Tried a few things to get it out with no luck. I will either bring it to a friends house and weld a nut to it just retap the hole.
Any other suggestions?

The picture of the wire is some of the past owners garbage electric work.
I also bought some pod filters to replace the past owners ugly POS DIY airbox.
IMG_20170511_113434.jpgIMG_20170511_115012.jpgIMG_20170511_115022.jpgIMG_20170511_115215.jpgIMG_20170511_120512.jpgIMG_20170512_154739.jpgIMG_20170512_154818.jpgIMG_20170512_161415.jpg
 
Just the engine and swing arm are left on the bike. One of these days I'll pull the engine and start cutting tabs and prepping for paint. Black Paint

Im debating on how to paint the engine.
As of now Im going just paint it all black with some satin engine enamel.

I have most of the components in for the new wiring harness but im going to wait until later to make it.

Going to clean the carbs soon.
IMG_20170522_212713.jpg
 
Double posted
 

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Pulled of the swingarm and pulled the engine from the frame. Next step is cutting any tabs that I will not be using.
Then Paint prep
Paint prep will include:
Sanding frame
removing chipping paint from engine
taping bolt holes off

Going to paint the frame, suspension, and motor black.
After paint Ill throw the engine back in and start on the wiring.
View attachment 7710
View attachment 7711IMG_20170620_193506.jpg
 
After 3 years, I'm back to working on the bike.
Got busy with school and traveling. Now I'm graduated and quarantine has bought me some extra time.

A little update as to where the bike is at:
I boiled the carbs and cleaned em out with carb cleaner. Also used a dremel to polish the float bowls.
I used some paint stripper to remove the old paint and am working on cleaning up the frame right now.
Tomorrow I'm gonna source and bend a pipe for the seat loop, get that welded on, and sand the whole frame for painting.
Pictures to come.
 
Small Update.
I went through and cleaned all the carb parts and just have to spray out the carb bodies with cleaner before putting them back together.
Frame is mostly stripped, just gonna go over it with a flap disk and clean up the small stuff.
Shown in the picture is one of the carbs. It was bent when I got it so I tried heating it up and bending it but that made it worse. Wasn't the most careful with it, but not too worried. Ordered a replacement for 50$ so no big loss there.
Still haven't sourced that tubing. Any suggestions? I'm thinking I'll buy a pipe and heat and bend it with a homemade fixture to bend the pipe around.

Next steps:
cleaning carb mounts and tubing.
Assemble carbs
Weld on tubing to frame
Final sanding of frame
prime and paint frame
Engine Work IMG_20200512_160447.jpgIMG_20200508_202042.jpg
 
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