1980 CB750K Cafe Project (hopefully)

[Griffin]

Hi everyone,

Like others I stumbled upon this forum looking for information on different things related to a potential 1980 CB750K build. I've just finished rebuilding the carbs and doing a tune up on my 1971 Moto Guzzi Ambassador. Now I'm looking to build a cafe racer. Interestingly enough I learned to ride on a 1974 cb175. That bike was sold to a family friend in the 80s. I recently called him up to see if he still had it so I could buy it back. Unfortunately the 175 is gone but as luck would have it he has a 1980 cb750k he's willing to part with. It has some issues but was parked in running condition a year ago. Front master cylinder is seized and a cam cover thread is stripped. I plan to put a helicoil in to fix the cam cover leak and rebuild or replace the master cylinder. The current owner is going to charge the battery Friday night and I'm going over there Saturday to see if the engine turns over and to check the compression. If all goes well I'll be bringing it home.

I learned a lot working on my old Guzzi, which has it's own story, but I'm just an amateur. I'm hoping I can fumble my way through the carbs and get this thing running again without too much trouble. Then I plan to break it down clean, paint, and polish everything. Might built a bump seat, lower the front a bit and add clubman bars. Not sure what size tires to get yet, I want it to corner really well though. Over time I will probably replace the air box with pods and add a 4 to 1 exhaust followed by re-jetting the carbs and tuning. That will definitely be phase 2 though. I'm looking for lighter, faster, better cornering and of course that cafe racer styling. Maybe for phase 3 I'll change the forks and swing arm, wheels, tires, and brakes. Of course that will be pretty far in the future!

I've already learned a lot reading this forum full of talented people. Feel free to reply with tips on tests I should do before handing over the cash.  I'll post some pics if it all checks out and I make the purchase! Really excited to get to work!

[TOOLS1]

Other then the pods (which never work, or even run as good as the original airbox) sounds like a good project.
TOOLS

[Griffin]

Thanks Tools I've read that before, so I know It's challenging. If I can't find evidence of a performance increase I won't do it. I've also read replacing the carbs can be a better way to go. I'm not opposed to that either.

On Feb 15, 2016 10:37 PM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

Other then the pods (which never work, or even run as good as the original airbox) sounds like a good project.
TOOLS

Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)

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[LukeM]

Funny you mention this. I just got the title transferred to me for a 1971 CB175.  If the deal for the 750 doesn't work out, and you're interested in my bike, let me know.  There's a posting of it here on our forum.

Maybe we can do some business.  I'm in the central Ohio area.
Luke M

[Griffin]

What a great bike! Looks exactly like the one I had! Awesome you got it running too. Ohio is a bit far from Delaware. Really hoping this 750 is not roached out.   Thanks for posting, glad I got to check out your 175.

On Feb 16, 2016 4:21 PM, "LukeM [via Honda CB750'S]" <[hidden email]> wrote:

Funny you mention this. I just got the title transferred to me for a 1971 CB175.  If the deal for the 750 doesn't work out, and you're interested in my bike, let me know.  There's a posting of it here on our forum.

Maybe we can do some business.  I'm in the central Ohio area.
Luke M

Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.

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[Truck]

You can always do what I'm doing, start with a frame and build your dream bike! There are enough aftermarket parts out there to build one of these bikes from scratch. Remember - Ebay and the interwebs are your friend.

[LukeM]

Thanks for the kind words, and good luck with your '750.  

Luke M

[Griffin]

That's awesome man! I'm not at that level yet, hoping by starting with a bike that's in decent shape my build will go nice and smooth. I love the gusto though do you have a thread for your build? I'd like to check it out.

On Feb 17, 2016 9:46 AM, "Truck [via Honda CB750'S]" <[hidden email]> wrote:

You can always do what I'm doing, start with a frame and build your dream bike! There are enough aftermarket parts out there to build one of these bikes from scratch. Remember - Ebay and the interwebs are your friend.

It's only illegal if you get caught.

If at first you don't succeed, use more lighter fluid

95% of Harley Davidsons ever made are still on the road... The other 5% made it home.

New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"

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[Truck]

Oh believe me, I'm not at that level yet either! I'm relying on my imagination, FSM Tools and Shiny...

I started a thread, but due to the insane weather around here I haven't had much time to do anything accept brainstorm and research parts. These bikes are pretty simple with a lot of aftermarket support. The only thing you really need to pull off a cool bike is a vision and the willingness to learn (and make mistakes).

Good luck, and post pics!

[Griffin]

Thanks man, good points! Saturday should be the big day getting excited, will certainly post pics.

On Feb 18, 2016 10:10 AM, "Truck [via Honda CB750'S]" <[hidden email]> wrote:

Oh believe me, I'm not at that level yet either! I'm relying on my imagination, FSM Tools and Shiny...

I started a thread, but due to the insane weather around here I haven't had much time to do anything accept brainstorm and research parts. These bikes are pretty simple with a lot of aftermarket support. The only thing you really need to pull off a cool bike is a vision and the willingness to learn (and make mistakes).

Good luck, and post pics!

It's only illegal if you get caught.

If at first you don't succeed, use more lighter fluid

95% of Harley Davidsons ever made are still on the road... The other 5% made it home.

New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"

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[Griffin]

I'm pretty discouraged about the prospect of using pods. I've read many many threads on people having trouble with them. What's amazing to me is that if you Google CB750 Cafe Racer images 2 out of 50 or so images have pods and a few have stacks. I wonder how many of those bike run poorly or are only setup for high revs.  I am fairly certain I'll keep the airbox, I'm just not confident in my ability to tune carbs when so many people have trouble. Someone posted a Honda racing doc on using flannels. I found that intriguing but those bike were only setup to be raced so again I wonder how well the ran at 1/4 - 1/2 throttle.

In any case I'm getting excited to get started.

On Feb 15, 2016 10:37 PM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

Other then the pods (which never work, or even run as good as the original airbox) sounds like a good project.
TOOLS

Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)

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[Truck]

First you have to look at the pics, are they DOHC or SOHC? Are they using stock carbs?. Look up Bread Boxes if you want something that looks better than stock. I've seen no hard data, but rumor has it the work on DOHC bikes.

[LukeM]

For best drive-ability (like everyday riding), it's best to use the factory air box.  These carbs like to have a fairly constant source of vacuum in order to run properly.  The air box is engineered to do just that: it restricts air flow just enough to provide that.  If you're into the cafe racer look, pods are the way most people go, but be prepared for LOTS of tuning and tweaking and so forth.  After all that, it still might not run as well as it would with the airbox in place.

My 2 cents worth: get the bike running with all the stock components in place.  That way, you have a baseline to go back to, in case the next thing you change causes problems.  2 more cents:  document your processes.  Digital cameras, notebooks, whatever works best for you, but document your work.  It saves headaches later.

Luke M

[Griffin]

That's the plan. I'm going to focus on running first, then basic styling followed by performance mods. Looking into exhausts now. Seems like the Mac 4 into 1 is popular. I'm sure that requires jetting too.

On Feb 18, 2016 1:08 PM, "LukeM [via Honda CB750'S]" <[hidden email]> wrote:

For best drive-ability (like everyday riding), it's best to use the factory air box.  These carbs like to have a fairly constant source of vacuum in order to run properly.  The air box is engineered to do just that: it restricts air flow just enough to provide that.  If you're into the cafe racer look, pods are the way most people go, but be prepared for LOTS of tuning and tweaking and so forth.  After all that, it still might not run as well as it would with the airbox in place.

My 2 cents worth: get the bike running with all the stock components in place.  That way, you have a baseline to go back to, in case the next thing you change causes problems.  2 more cents:  document your processes.  Digital cameras, notebooks, whatever works best for you, but document your work.  It saves headaches later.

Luke M

Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.

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[Griffin]

Truck,

Thanks for the bread box tips. I'm having trouble finding them for the dohc bikes. I've found some cool looking custom ones though.

On Feb 18, 2016 1:03 PM, "Truck [via Honda CB750'S]" <[hidden email]> wrote:

First you have to look at the pics, are they DOHC or SOHC? Are they using stock carbs?. Look up Bread Boxes if you want something that looks better than stock. I've seen no hard data, but rumor has it the work on DOHC bikes.

It's only illegal if you get caught.

If at first you don't succeed, use more lighter fluid

95% of Harley Davidsons ever made are still on the road... The other 5% made it home.

New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"

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[Griffin]

I did find this company manufacturing them.
http://www.steeldragonperformance.com/air_boxes_7.html

I like the machine finish style.

On Feb 18, 2016 9:43 PM, "Dave Arnold" <[hidden email]> wrote:

Truck,

Thanks for the bread box tips. I'm having trouble finding them for the dohc bikes. I've found some cool looking custom ones though.

On Feb 18, 2016 1:03 PM, "Truck [via Honda CB750'S]" <[hidden email]> wrote:

First you have to look at the pics, are they DOHC or SOHC? Are they using stock carbs?. Look up Bread Boxes if you want something that looks better than stock. I've seen no hard data, but rumor has it the work on DOHC bikes.

It's only illegal if you get caught.

If at first you don't succeed, use more lighter fluid

95% of Harley Davidsons ever made are still on the road... The other 5% made it home.

New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"

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[Truck]

Those look good. I personally like the duel ones, but not sure if they would work on CV carbs.

You can also check Ebay, lots of parts, and usually good prices.

[Griffin]

I've emailed the company asking if they offer tuning suggestions.  I'll post their response. The duel ones do look cool but I was thinking having all the carbs share one box would be better since these things are so touchy. 

On Fri, Feb 19, 2016 at 9:31 AM, Truck [via Honda CB750'S] <[hidden email]> wrote:

Those look good. I personally like the duel ones, but not sure if they would work on CV carbs.

You can also check Ebay, lots of parts, and usually good prices.

It's only illegal if you get caught.

If at first you don't succeed, use more lighter fluid

95% of Harley Davidsons ever made are still on the road... The other 5% made it home.

New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"

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[Griffin]

Just heard back from them.  They said they have customer feedback with recommendations on re-jetting they can share.

On Fri, Feb 19, 2016 at 11:02 AM, Dave Arnold <[hidden email]> wrote:

I've emailed the company asking if they offer tuning suggestions.  I'll post their response. The duel ones do look cool but I was thinking having all the carbs share one box would be better since these things are so touchy. 

On Fri, Feb 19, 2016 at 9:31 AM, Truck [via Honda CB750'S] <[hidden email]> wrote:

Those look good. I personally like the duel ones, but not sure if they would work on CV carbs.

You can also check Ebay, lots of parts, and usually good prices.

It's only illegal if you get caught.

If at first you don't succeed, use more lighter fluid

95% of Harley Davidsons ever made are still on the road... The other 5% made it home.

New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"

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[Griffin]

Picked up the bike today! Here are some pics. I'll be selling the seats, sissy bar, crash bar, and maybe a few other things once I get a cafe seat and cut the rear.





And one of my Guzzi just for fun.