1979 CB750 DOHC Monoshock Build

bananas

New Member
Hello DTT! Long time lurker on the forums. You guys have been a huge inspiration for starting a build.

I've been meaning to post a build thread for my 1979 Honda CB 750 Limited. Picked her up two years ago for $200. She was abandoned outside of a building downtown and sat for 4 years.

My original intention was to convert her into a very clean Cafe Racer but during the course of the build it has progressed into more of a cafe-inspired muscle bike. Much of the build is designed to focus its visuality around the prominent air cooled Inline 4. In the handling department, she'll receive a ton of weight reduction, a bit of frame strengthening, modern forks, swingarm, brakes, wheels and a custom rear monoshock suspension. Next I'd like to do race carbs, a front-mount oil cooler setup and custom GP exhaust system.

A full build write-up will be posted here as she gets nearer to completion. Don't want to spoil the suspense :)

I'll include a list of parts/modifications for reference (and for my own inventory). This will be updated as the thread goes along. The list includes both installed and acquired parts.

Performance

-Freshly Rebuilt Motor
-K&N RC-0790 Air Filters
-K&N Vent Filters
-Honda RSC (Racing Service Center) Carb Modification (Coming next)
-1992 Honda CBR 600 F2 Coils
-NGK Sparkplugs
-Moto Guzzi V11 Sport 9-Row Oil Cooler
-Custom 16T Off-set Front Sprocket/ Driven 42T 530 Power-Up Sprocket Conversion
-4-1 2.5" Exhaust System (Temporary Setup)
-2" DEI Exhaust Wrap, Graphite-Black
-Shorai LFX14L5-BS12

Suspension/Handling
-2001 GSXR 600 Front Forks, Racetech Springs and Emulators
-2001 GSXR 600 Triples with 1979 CB750 Stem
-2004 GSXR 750 Front Wheel/ Rotors
-2001 GSXR 750 Stabilizer, Pro-Tek Fork Mount, Custom Frame Mount, Fork Oil Mod
-2001 GSXR 750 Front Calipers/ Master Cylinder
-2001 GSXR 750 Swingarm, Custom Strengthening, Custom Shock Mount
-2006 Ducati SuperSport 800 Rear Shock, Heavy-duty Spring, Custom Mounting
-2004 GSXR 750 Rear Shock. OEM Mounting.
-2004 GSXR 750 180 Rear Wheel, Rotor, Custom Races and Axle
-2001 GSXR 750 Rear Caliper/ Master Cylinder/ Reservoir/ Brackets
-All Balls Racing Steering Bearings
-EBC HH Brake Pads
-K&L 90° Valve Stems
-Michelin Pilot Power 3 Tires

Controls
-Trailtech Vapor Stealth Gauge/ Indicator Dashboard, Custom Housing
-Tarozzi Rearsets, Custom Mount and Brackets
-2001 GSXR 600 Brake and Clutch Perches
-CRG RC2 Levers
-Renthal Ultra-low 7/8" Superbike Bar
-7/8 Tag Metal Bar Risers, 1" Rise
-Domino Racing Push/Pull Throttle
-ProGrip 780 Sportbike Grips
-Low-Profile Minimal Left Switch
-POSH Factory 7/8" Dual "Cap" Switch
-Marine Turn-Key Ignition Switch

Misc
-1980 Honda CB 750F Tank
-LSL Clubman Ø6.5" Headlight
-LSL Headlight Brackets
-Radiantz 8.2" LED Turn/Brake Z-Flex Array
-LED Front Signals
-Motogadget M-Unit V.2 Electric Control Unit W/ Custom Wiring Harness
-Stainless Engine Bolt Conversion
-Adjustable Anti-Vibration Longstem 4" Mirrors
-7/8" Universal Mirror Mounts
-Shinyribs DOHC Tach-Plug "Flat-Top"
-Custom Lightened Subframe

Missing/ To-do
-Stainless Brake Lines, Front
-Front Reservoir
-Seat Pan & Alcantara Upholstery
-Battery/Electronics Box
-Rear Brake Pads
-Front Fender
-Rear Hugger
-Exhaust

I've never actually built anything before so it's a learn as I go process. For now I'll be outsourcing anything that's too difficult.

This is a picture from the day I picked her up. (Yes, I now know that's not the way to tow a bike)



Full engine rebuild performed by Cypress Motorbike in Delta, BC. After four years of sitting we pretty much had to replace everything. Clubman bars installed (and now removed). It's at this point I realize a cafe-racer is not for me. Way too uncomfortable (I'm 5'6) -- especially for a 566lb monster of a bike! Rode around the parking lot and realize I'm unhappy with the suspension and braking system. Also she desperately needs rear-sets.



Bike sitting in my garage (excuse the mess!). Seat, fender and hugger removed. Temporary bracket and Tarozzi rearsets installed. Time to detab and cut the rear frame.



Mostly de-tabbed bike and rear frame has been cut off. Test fitting of the new rear loop and taillight. The shin destroyer engine guards will be removed a little later but for now they are great in case the bike falls over.



The frame is feeling a bit long. To achieve the look I'm going for I think it should end exactly above the rear axle. More cutting to do!



Applied first layer of paint remover to the tank. Test fit back on the bike. Metal tank on black motor, frame and wheels?



Another View.



Obligatory ass shot.



A couple more applications of paint remover and about an hour of sanding with an orbital. The frame has been cut shorter and the battery box and wiring harness are now removed. Test fit of a new Shorai LI battery.



Another shot. I'm liking the stance but still unsure about that tank. Too fat?



Front end, carbs, airbox mostly removed. Curious how the new tri-spoke wheels will look on the bike. 2001 GSXR 750 rear wheel on Michelin 2CT tires.



New front end installed. New tank from a 1981 CB750F. Had the original steering stem pressed into the modern lower triple. The entire front end comes off a 2001 GSXR 600 for ease of installation. The forks are off a totaled race bike and have Racetech springs and emulators installed. Originally I had wanted to do a USD fork setup but I think these forks match the style of the frame a bit better. Sanded a bit of the old paint off the motor. Currently deciding whether to go with a Rental Super-bike bar or clip-ons. The bike sits about 1.5-2 inches lower with the new front end so it looks like I'll need a custom exhaust setup sooner than later. In the background is a buddy's 197- KZ200 build.



New LSL headlight and mounting ears. Trail Tech Vapor Stealth gauge and indicator dashboard.



Tested my luck purchasing a set of Ebay Pazzo-style levers. They fit. Unfortunately they also pre-load my brakes. $40 in the garbage. Oh well, lesson learned. Purchased a set of CRG RC2 levers instead.



The bike is off at a machine shop getting a modern swingarm (2001 GSXR-750) and rear monoshock (2004 Ducati 900SS) installed.



That's it for now!
 

cliffno350

New Member
Re: 1979 Honda CB750 DOHC

Yup looking good, a way lot better than inferior bike Chris so and so tried to pass off as a build
 

Hoosier Daddy

Earache my eye...
Re: 1979 Honda CB750 DOHC

Nice that you are bringing her back from the slow death outside. Interesting stuff so far! Can't wait to see the monoshock swinger when it gets back.
Soooo... You striped the factory LTD tank and then didn't use it? Hope it wasn't as nice as it looked in the pics. :( That and the side covers would have fetched a pretty penny on ebay.
 

bananas

New Member
Re: 1979 Honda CB750 DOHC

Hoosier Daddy said:
Nice that you are bringing her back from the slow death outside. Interesting stuff so far! Can't wait to see the monoshock swinger when it gets back.
Soooo... You striped the factory LTD tank and then didn't use it? Hope it wasn't as nice as it looked in the pics. :( That and the side covers would have fetched a pretty penny on ebay.
Unfortunately the paint on the tank was pretty evenly pitted all around. Early on I contemplated doing a resto but decided against it.. Recently I saw a showroom condition LTD sell on ebay for $6500 -- kind of regretting it now haha. The side covers are sitting in a bin of parts which will be listed for sale once I take pictures of everything :)

Minor update for today:

Swinger is attached. Was able to use the original Honda swingarm pivot and axle. Still missing a couple of parts before she can be a roller. At the moment the rear wheel is a bit off center -- I'll be looking for an offset front sprocket.. anyone have any advice?


Next up is fabricating shock mounts for the Ducati 900SS shock. Currently deciding whether or not to cut and fab a new rear subframe. Also, hydraulic rear brakes :)
 

SaltCityCafe

New Member
Re: 1979 Honda CB750 DOHC

Yup I'm digging that rearend...my next project is going to get crazier buy since my current 750 is my first build I'm not getting to nuts
 

vbtravisd

New Member
Re: 1979 Honda CB750 DOHC

Nice! I have this bikes older brother! I just fitted up my 08 gsxr swingarm on my 78 last night. Looking good man...
 

rundown

New Member
Re: 1979 Honda CB750 DOHC

Very nice build so far. did you have to do any machining on stem, or was it just a question of pressing out the old and press in the Honda stem?
 

bananas

New Member
Re: 1979 Honda CB750 DOHC

rundown said:
Very nice build so far. did you have to do any machining on stem, or was it just a question of pressing out the old and press in the Honda stem?
The 2001 GSXR 600 stem was about 1mm larger than the CB750 stem. We ended up welding on a bit of additional material. A pin was added through the GSXR triple and the CB stem just in case. I'll get a picture of it when I update!
 

bananas

New Member
Re: 1979 Honda CB750 DOHC

Update:

New subframe and rear hoop welded on. Ducati 900SS Rear shock installed.


Originally I had wanted the shock mounted to the top of the swingarm brace like older non-linkage bikes (like the 900ss). However, without a way to test, and unwilling to compromise a testicle, we decided to mount it below where the aluminum is stronger. A bit of extra bracing was added here just in case.


Shot of the new rear :) The upper mounting point is just under the tank and in-front of the seat. As the original shock was a non-linkage setup we were able to mount directly to the frame.


I had ordered a set of Tarozzi rearsets which were supposed to be direct bolt on. Unfortunately either I got the wrong kit or they don't make kits for the Limited models (This would be my assumption). Either way, next up is a custom mount for the rearsets. Also a bit of bracing will be installed into the frame to compensate for the modern rubber.
 

bananas

New Member
Re: 1979 Honda CB750 DOHC

So I'm starting to think the bike is a bit too low to corner properly (currently 3.5") so the upper shock mount is getting lowered by about 4 inches. A custom exhaust system (which I didn't plan on doing yet) is probably going in pretty soon to offset the lower ground clearance from the new front end. Luckily the footpegs have been removed in favour of rearsets so we've got more options. I'm thinking we may be able to fit two 2-1 exhaust systems, one on each side which travel parallel to the lower frame rails while hugging the case covers. We could either have the pipes end just past the rearset mounts or have them terminate on a vertical axis next to the swingarm. Should be interesting!
 

bananas

New Member
Re: 1979 Honda CB750 DOHC

Another thing, I've planned to add a steering damper as a safety measure so I picked up a stock 2001 GSXR 750 unit hoping to use the stock lower triple mount along with a extra large steering stop. Turns out the unit isn't long enough to fit.. tried a bunch of locations as well.. Anyone know a decent (and relatively cheap) steering damper that is somewhat longer than usual? I'll mount it under the headlight on the front end or perhaps somewhere on the frame..
 

bananas

New Member
Re: 1979 Honda CB750 DOHC

Jrbrownie00 said:
nice work with the mono, keep truckin.
Thanks! It ended up being a bit more work than I had hoped.. but it's getting there! ;D

canyoncarver said:
I'm in. Keep at it.
Thanks! 8)


Minor Update:

Rearsets mounted. Shock lowered a couple of inches with a stiffer spring on order. Hopefully this adjusted suspension setup will perform better. Ground clearance is now about 5.5".



Next up is bump stops, handlebar and risers and new ignition mount!
 

bananas

New Member
Update:


Shock installed with a new spring. A bit stiff but otherwise working great! It may still get moved if need be to improve handling but hopefully not. he old 120 rear wheel is now a perfect 180 setup. The swinger is attached perfectly in-line and on-center (not an easy task at all). As much as I love my other build I dont think any of my toys make me smile as much as this one. :) I've also updated the first post with a parts list and info.


Next up will be learning how to make a custom wiring harness (looking at a Motogadget setup -- I guess the ramen diet continues for bananas...), an RSC race carb-modification, tuning for larger jets with K&N air filters and finally, a temporary muffler setup. A Fibreglass/Kevlar seatpan and upholstery come next along with a battery and electronics box.


Check out that new beef in the rear -- finally balances out that massive 300lb inline four.



New shock angle with heavier spring. We'll see how she handles. Rear brake and linkages all set up with custom brackets and mounting. I'll be making a custom heel guard soon out of CF/fibreglass.



Extra angle:
 

trek97

Active Member
DTT BOTM WINNER
Its looking really great. Have you tried fitting the chain to it ?
The swing and tire are monsters.
 
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