Fresh '82 CB750 Build

[nico750]

Hey guys, figured I would share CB750 build with the forum. It has been an interesting one.. I'm typicaly a little more of a car guy but I was in Miami one day, saw a cafe racer and fell in love. I looked at it sitting there in my girlfriend's grandmother's parking garage; and knew I had to have one. So I began searching, and working like crazy until I found the one. I didn't get one of those $500 steal deals like I see a lot of you guys score on, but I think what I found was a decent package.


It was a 1982 CB750C, pretty much a rolling chassis.
It came with :
Hayabusa forks w. clip on handlebars already installed..
brand new Takasago Excel rims,
brand new Avon Roadrider tires,
Tokico 6 piston caliper brakes,
a custom fuel tank from a '77 750,
extremely clean keihin factory carbs,
along with another set of Mikunis (still debating if I'm going to use these later on or not)
freshly gone through 750 motor, and another motor I still need to go back for.
Oh how could I forget, it also came with a CB900 oil pump, oil pan, oil cooler, and a CB900 cam I will be installing later.

I'm gonna be honest, I ended up paying $2k for the set up. But when I got there and started looking at everything & doing the math in my head, this is actually a pretty damn good deal.


So the build has been pretty fun, and also a bit of a learning curve. Things have been smooth sailing, all the way up to the wiring. I also have a rear set issue/dilemma that I've been trying to figure out since I first bought the bike. Not a fan of the factory setup at all. Time to share (I also have a few questions)

How she was when I first brought her home..

Purchased some fairly inexpensive hand controls, throttle, and grips off of amazon. They seem pretty decent, only time will tell if they last

Here's the motor I plan on dropping in, still have to clean it up some with a little black paint and polishing

I wanted to see what she looked like at night

After a short delay, finally got moved into the new place. I really enjoy taking pictures of this bike, if you can't tell. Haha

Little selfie shot.. I'm 6'1 so I wanted to see how if I looked like a clown on a children's bicycle. It actually fits me pretty well

Stripped down, grinding off the unnecessary junk.. no I didn't do this in my living room. It was definitely in my spare bedroom

Managed to get the motor in all by myself. With some help from the carpet (not scratching anything from laying it on its side)

Getting there. ..yup - this is my "garage" although, its usually a little more organized.



I will keep you guys updated frequently. I would like to have it ready for paint by the end of the month. My goal is a test ride on my birthday, August 30th. I do have some questions/advice needed. I will save them for the next post

 

[nico750]

So I'm getting down to the wiring on the bike. I bought a manual for it, but it doesn't specify everything

I've been trying to find a source to figure out these tabs on the solenoid. I'm guessing they are just connections - 2 for the battery side and 2 for the starter?

Can anyone direct me where to find this mounting bolt, or give me specifics so I can just buy a non spec bolt to run through it?

I'm guessing red, and red w white stripe go to battery, and the other two go on the starter side? (on the solenoid)

The bike came with a universal 4 wire, three point (off/acc/on) ignition switch. But I can't find a diagram for what wires lead to what. I'm hoping someone is familiar with these and give me a direction?

Any and all help is appreciated guys, thanks in advance!

 

[Skelee]

This may helphttp://cloud.tapatalk.com/s/5b71be978f3ee/Wiring_Diagram_CB750SC_82__(1).pdf

 

[Wez_]

That motor mount bolt has a bushing or spacer to make up that gap, just FYI. You may find the bolt, or simply a replacement, but that spacer is likely needed to keep the engine from vibrating excessively.

 

[nico750]

Skelee - I have a wiring diagram like that in the back of my manual, but I appreciate your help. I'm trying to figure out what the connections are for on the solenoid itself. There aren't really any details.

Wez - Yes I have the spacers in my crate of parts. Thanks for the heads up though.


I just ordered the foot pegs for it, and I'm in the process of cutting some steel bar to make rear set brackets. Then I will be calling a local mobile welder off craigsist to put those on, and also weld on some SOHC style brackets for passenger pegs. Couple more small weld mods and I will be stripping down for paint.

 

[Dave]

Dude, in the house!

Okay, I once parked my bikes in the kitchen but...

Buy a sheet or two of 3/4" sanded plywood to lay on the floor and put the bike on. When your done, you can use the wood for shelves or a work bench.


2k investment and your going to put that crap wiring in it? Buy a new wiring harness.

 

[nico750]

Haha, yes in the house. I don't have a garage or easy access to one where I could work on the bike as I please, so the spare room will do. I have a junk rug down to protect the floor. And I'm not doing any engine work in there, just basic bolt on stuff. So it's really no different than building a bicycle! ..or something like that lol

Crap wiring? Whats wrong w the wiring? After unwrapping the harness, all the wires are good as new. The largest factor is budget, but plug and play is nice too. I still may buy one, but I really just want to get it put together and get it going. That's nothing to change out after its built.

I'm in the process of coming up with the brackets for the rear sets.. and would like some opinions on what you guys think is best. The simple welded tab off of the frame is definitely the easiest route, but I'm wondering if that is going to cause the pegs to sit too far in. My second idea is that same bracket, welded to a simple tab welded straight out, then 90 degree welding to that. Lastly, I've thought of making my own version of cognimoto's brackets bolted off of the motor mounts. I will include some photos more better reference.

 

[nico750]

Any input is appreciated!

I want to keep the rear hoop long enough for a passenger, so my girlfriend and I can ride around when we go to Miami - but this looks a little far out. Or am I crazy? I zip tied another hoop, with the desired length. Do you guys think it is too short / or as it is - too long?

 

[nico750]

 

[nico750]

Starting to actually look like a motorcycle

 

[Dave]

I want to keep the rear hoop long enough for a passenger, so my girlfriend and I can ride around when we go to Miami - but this looks a little far out. Or am I crazy? I zip tied another hoop, with the desired length. Do you guys think it is too short / or as it is - too long?

Post a photo of your girlfriends, um, seating area, and we'll let ya know. (I could not keep a straight face while typing that LOL) j/j


OK, serious now. Having a passenger totally goes against the "café racer" theme. Racing seats aren't for sitting on, they are padded areas you brace your legs against while, well, racing.

The stock seat doesn't give the passenger much to sit on already, if you want your girlfriend to ride with you for longer then 5 minutes I wouldn't make it any smaller.

 

[nico750]

Haha clever one. I don’t much care about the “cafe racer theme”. But I will never understand the concept of owning a motorcycle that you can’t put a woman on the back of! I appreciate your input and I will be leaving the length! Dan, do you have any opinions on the rear set mounts I posted? I appreciate your input !

 

[Wez_]

You cant mock up the rear frame hoop without your seat. I mean, it's possible, but you will likely make some final trims, cuts and welds with the seat installed. I would look into your seat/pan, then finalize the hoop. You'll want to throw a level across the hoop and ensure it's level.

 

[nico750]

I have the factory seat still, which fits like a glove. So I’m either going to strip that down to just the pan, and build it from there or start from scratch - wrapping the frame w Saran Wrap and fiberglassing it.

Wez , did you get that seat from eBay? I almost bought one just like it

 

[Dave]

I really prefer the stepped seat to the flat ones.

#1 It keeps my butt from sliding on/off the seat under hard acceleration.

#2 It raises the passenger up a bit so it's easier for her to see past you and it provides her with a thicker, softer seat.

#3 (This is an odd one) The standard 6 hook bungie net fits perfect on the raised part. It would fit too loose on a flat seat.

This is all just me. Perhaps you should temp mount the seat and have her sit on it with you. Would you buy a chair you were going to sit still in without testing it first? Plus, think of how she'll react to you taking her comfort into consideration when choosing the seat for your bike

 

[nico750]

Oh, I definitely prefer the stepped seat. The zip tie mock up is just to get an idea of the length difference. I think I'm going to stick with the loop that is on there.

 

[nico750]

Do any of you guys happen to have a photo of the way your fuel lines are ran? There are two lines coming off the carb, but only one has a filter. Does the one line feed all 4 carbs?

 

[nico750]

I think I got it figured out. One is the line for fuel and the other “mysterious t” is the float bowl vent.

 

[pidjones]

If you haven't figured out you solenoid yet; red and red/whit go to the two top lugs in your photo an are alway powered from the B (battery) terminal. The bottom two lugs connect to yellow/red and green/red to activate the solenoid.

BTW, my GL1000 has a fiberglass seat pan that I scored on ebay. Looks like someone used a bare pan for a mold. It even has the holes for the bumpers and mounting nuts glassed into it. I used spray glue (77, I think) to build layers of carpet foam to the shape that I wanted - trim with electric carving knife -, then had an upholsterer cover it.

 

[nico750]

Yep, I literally just figured that out in the past day or two. Lol. But I’m not getting ANY action from it. No clicking. No nothing. Could this be because of the neutral/brake/clutch safety switches? I don’t have the bike fully wired yet. The only thing that happens when I hit the start button is the green(neutral) and yellow(oil) like lights light up. Thanks for your help.

Ps: your pan looks great! I will be doing a fiber glass mold myself, but doing it from the frame. My tank swap blocks me from being able to use the original seat pan I believe.