Topic: My cb750 cafe project.

[Mortum]

Well here are some pics of my cb as she sits now.







A little history on the bike. 

A friend of mine was given this bike by the original owner. The carbs where froze, tank was rusty on the inside, brakes where shot, fork seals bad, paint faded, and a little surface rust on all the chrome stuff.

My friend paid for all the parts and I tore her down and redid her from the frame up. The engine still had great compression so I left it alone other than a few gaskets here and there along with a valve adjustment. Then I laid some black paint down for him and took care of the inside of the gas tank. 

He rode it a total of 100 miles and let her sit in his garage for 2 years. He asked me if I wanted the bike since he was needing a little money. What did he want for it?  500.00 so I bought it.

I just went back through the carbs and got her back on the road. The pics above are how she looks right now. You can see where gas has leaked all over the case. Thats taken care of now lol.

So now for my questions.

1. I am thinking about going through the engine and doing a 836 build will it still be a reliable runner that I can jump on and take off for the weekend? If not Ill leave it as is.

2. Can I run a 75 gas tank on her?

3. I thought I was going to buy most of my stuff from Carpy but after reading some post on here...Should I buy parts from him or sorce them from someone else?

The reason I ask is there are a few parts I am ready to buy this week or next and he hasnt got back to me with questions I have about ordering from him. So that kinda makes me shy about just ordering off his website and paying for the stuff right away.

4. I want to run a rear disk and not sure what year cb to take the donor parts from. So what year cb's can I rob the parts from?

Any other things you guys think I need to know throw it at me. I am open to sugestions and knowlege from other people.

Im not new to bikes and am a pretty decent fabricator but i want to keep every thing I do bolt on. Or at the most where I would have to weld brackets back on to put her back to stock apperance if I ever wanted to .

Thanks in advance guys.

Kip

[KB02]

That is a nice lookin' bike, Kip. Just clean up that gas leak stain and she'll be a real beaut!!

An 836 kit? A lot of people run them. As long as you built it correctly, you'll have a great motor that will be perfect of weekend trips (or playing around). Take your time, put the money in and build it right. It's when corners get cut that things tend to go wrong. I' building the Cycle-X 850 kit myself... and buying a house, so the engine is taking a bit of a back seat at the moment...

Can you run a 75 tank? Yes, but it won't sit against your seat as well as the stocker does.

Rear disk? F models ran a rear disk, so you should be able to grab an F swing arm and rear to put in. The 75-76 F used a spoke wheel like you have. I believe the 77-78 F's used the Comstar rim.

As for Carpy, You'll find mixed emotions about the man here. Personally I like what he does, I like his products, and if he sold something I wanted I wouldn't worry about ordering it from him. Others would disagree. There are other vendors out there.

[doobiebro]

Nice looking bike and a great buy at $500!

I have a Weisco 836 kit in my 1977 750K and really like it.  It pulls strong and loves those high rpms.  Although, the stock bore is still a good strong engine.  You may consider a one over bore with some head work.  Or, if you combine the 836 kit with a mild cam and port and polish the top end, it will still be very street rideable, but quick.  A more radical cam is better for the drag strip.

As KB02 stated for a rear disk, use the 75-76 F model to keep the spokes.  Using the F model swing arm avoids the need to weld any brackets.  The F model swing arm is one inch longer than the K model, so the steering geometry will be affected slightly, although probably not enough to notice.

[Mortum]

well it will be a 836, cam, larger intake valves, aftermarket rods, and under cut gears for sure. Still trying to figure what all else I need for the build. Since the engine that is in her s still good Im going to build one of the engines I picked up then swap them out so I dont miss out on a lot of rideing time.

[eurban]

Mortum-

A few thoughts . . .I like the late engines as a basis for performance builds.  They have all of Honda's refinements, including a better breathing head, and improved clutch.  You might want to consider this as you choose which motor to build up. . . . . The vast majority of your braking power will be done up front so adding a rear disc won't do too much to help with braking performance.  For braking improvements, consider either doing everything you can to maximize the braking abilty of your stock disc / rotor, or installing dual front calipers / discs.  You can rebuild your caliper and master cylinder (or perhaps install a modern master) and install stainless braided lines to you stock setup.  New quality pads and a properly adjusted and functioning brake arm will help too.  Dual discs with spokes could be either adding a second stock style caliper / rotor or grafting on a different set of front forks etc.  The early GL1000 front end gives stouter forks, and dual disks with spoke wheels.  The GL trees fit the 750 headstock. . . .  .You previously were wondering about the 836 as a reliable runner to "take off for the weekend."  An 836 motor can certainly fit this need well but you need to consider the nature of the motor you want to build.  Do you want a max HP high RPM screamer, with a narrow powerband, or a lower HP, torquey engine with wider power band?  Your choice of larger valves and aftermarket rods would indicate you are going to build a screamer.  A mild performance cam and mild port job, combined with the bump in displacement and compression from the 836 would give a nice HP improvement over stock as well as a wide power band that makes good power at 5K RPMs right where you are cruising at on the highway.  An engine in a milder state of tune will likely be more reliable and won't cost as much to build. This BTW is the aproach I took and I couldn't be happier with the results. Just something to consider.

[Mortum]

really a torquier engine with nice power across the board is what Im after.

I am going to go to a dual disc set up in the front and as far as the rear goes if I find all that I need to I will do it also.

I did think about swapping a more modern front end onto the bike but I want to keep it some what period correct as far as looks go.

Thanks for all the advice you guys are opening my eyes to other directions I didnt think about.

[eurban]

75 / 76 GL front end looks pretty period correct. . . .



Here's a full shot of my "cleaned up" 78k with the stock pipes, seat, tank and Gl front end.

[plastikjock]

Front end swap looks great.  I am doing a similar thing on mine - cb750f2 forks, which I believe use the same calipers as yours. Did you have to reduce the diameter of your discs to suit? Or if you used the Gl wheel / disc what is the disc diameter? I think by roughly lining mine up, I am looking at reducing my disc diameter by 20mm to approx 276mm OD.

Or am I talking total crap and the gl forks have the same caliper mounted higher up to allow a bigger disc?

Cheers

 

[eurban]

I used the entire GL front end, including rotors.  I can check the diameter of the GL rotors tonite, but I can tell you now that the GL forks are spaced a good bit farther apart than stock 750,  and if you mounted the GL rotors to your hub (hub itself essentially the same between the 750 and GL) they would interfere with the 750 fork legs.  Basically they are offset farther away from the hub than the stock 750 rotors. 

[plastikjock]

After searching for ages I found a diameter for cb750f2 discs - 276mm. So my guess was right, as the discs I have are 296mm, need to machine away 10mm. I only need to space the calipers away from the fork approx 2mm to get them to line up axially. My only fear is the disc thickness is greater, but it should be ok.

Thanks anyway.
 

[bzr]

Wow, that is #$%*in'!

Every day I'm impressed by the quality and caliber of work on here. (Really makes me look like a slacker.)

[Mortum]

well I am now looking for f front end along with the rear or a gl front end and f rear. I did get two 75 tanks yesterday. So I will be stretching a tank here in the next few weeks also.