1979 Honda CB 750 Cafe-Fighter

[bananana]

Hello and welcome!

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.


A bit of history. The Honda CB750 was introduced to the North American market in 1969. Known as the first Superbike, it was the first mass-manufactured air cooled inline-four production bike and the first to offer hydraulic dual-disc front brakes. With its incredible reliability and a 120mph(190km/h) top speed, the CB750 was hailed as Honda's masterpiece. At its release, Cycle World called it "The most sophisticated production bike ever". By no means a rare bike, in fact, one of the best selling of all time. Over 500,000 were built. A testament to Honda's build quality, quite a few still run to this day.

In 1979 Honda released the new DOHC model. To celebrate the 1969 launch of Honda's best-seller, 5000 "10th Anniversary Edition" bikes were produced for the US market. Although not as popular as the SOHC bikes built from '69 to '78, the DOHC bikes have a smoother power delivery and a power bump up to 77bhp @9000rpm and 48ft-lb tq. A 5Sp Wet Clutch transfers power through the 120 Comstar rear wheel. Stock weight is a colossal 566lbs wet.


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 very 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 direct-link monoshock suspension. Eventually I'd like to do race carbs, a front-mount oil cooler setup and custom 2x 2-1 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 Offset Front Sprocket/ Driven 42T 530 Sprocket Conversion
-RK XSO 530 Chain
-4-1 2.5" Mac 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
-[REMOVED]: 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
-Biltwell Recoil Grips
-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
-H4 LED Headlight Bulb
-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. 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 -- especially for a 500lb 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 (2006 Ducati 800SS) installed.


That's it for now!

[boatcaptain]

are you able to insure the bike??
Posted via RS Mobile

[bananana]

Yep! Although she will need a appraisal and inspection before hitting the road.

[jaemc]

Looks great! I've always wanted a bike like this as well. Something different from allt he crotch rockets. Keep it up!

[BillyBishop]

Love it, keep it up! Tank might seem a little fat right now, but I like it. After you mock up a seat it'll look different as well.

Definitely just what I needed to see to force myself back into my frigid garage and work on my bike. I too have been keeping my eyes out for a newer front end for a decent price but no joy so far!

[bananana]

Originally Posted by BillyBishop

Love it, keep it up! Tank might seem a little fat right now, but I like it. After you mock up a seat it'll look different as well.

Definitely just what I needed to see to force myself back into my frigid garage and work on my bike. I too have been keeping my eyes out for a newer front end for a decent price but no joy so far!

I'm glad the thread has inspired you . We definitely don't see enough custom builds in Vancouver. I'd love to hear more about your project!. The build is also posted on Do The Ton and Custom Fighters where I've been getting most of my inspiration and info for the build.

I was at Modern picking up some missing bolts a couple of weeks ago. I'm not sure if it's still around but they had a full front end and wheel from a totaled late 90's GSXR 1000. They offered it for sale for $150 -- thought that was a pretty good deal.

[hud 91gt]

Is the new tank a different shape? Loved the bare aluminum look! Have fun!

[bananana]

Minor Update:

[bananana]

More Photos:

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. Next up is fabricating shock mounts for the Ducati 900SS shock. Currently deciding whether or not to chop and fab a new rear subframe.

[Zedbra]

That's a big change - it's looking great. Looks like you will be needing some subframe fab work to mount a uni shock. Keep up the good work, looking forward to seeing some more updates.

[jaemc]

Sick. When you're finished we gotta re-film Kanye's bound music video

[bananana]

Update:

Installed a new offset 16T front sprocket and a Driven racing 42T rear on a 530 chain. I'm hoping this will provide enough low end-grunt but I'm starting to think I should've gone much higher. The stock CB was *18-38 with a 630 chain. (*It's actually 15T, Doh!)

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

[bananana]

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!

[bananana]

Update:

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

[BillyBishop]

Looks like it's coming along well man! Think it'll be ready for the spring meet? Or will you bring your Duc for that?

[bananana]

Originally Posted by BillyBishop

Looks like it's coming along well man! Think it'll be ready for the spring meet? Or will you bring your Duc for that?

Thanks! Unfortunately I'll be away during the meet.

I'll bring one of them to the summer meet!

[?NR]

great build! keep the updates coming and hope to see this beauty soon !

[z3german]

Sweet build man!

[bananana]

Originally Posted by jaemc

Sick. When you're finished we gotta re-film Kanye's bound music video

Goddamnit it James you sick bastard. I just watched this.... only if you're the chick!

[bananana]

So it looks like my shock placement is all off. Unfortunately there will be lots of maths involved in my future. I'd prefer not to play the trial and error game when my testicles are on the line.

Anyone with a good understanding of shock geometry out there?

I'm using this as a reference.

[bananana]

crap, please delete.

[bananana]

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. The 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. Also, I've updated the first post.

Next up will be learning how to make a custom wiring harness (looking at a Motogadget setup), 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:

[bananana]

Since it's been getting real nice over here I've been thinking... what if, as a temporary setup, instead of build a custom exhaust system I just welded a baffle directly onto my 4-1 pipes? Would this provide enough back-pressure? Will it be too loud? Does this even make sense?

[320icar]

Just go get some random oem muffler, chop it to about 1/2 length and slip it on to your 4-1 as a quick 2 hour project. Should sound killer and be cheap as hell

[bananana]

I've been getting a ton of questions about my monoshock setup on other forums. Figured I'd update this thread as well in case anyone's curious and wants to learn from my mistakes.

Fitting the GSX-R swingarm wasn't particularly difficult. The stock axle actually just kind of... fits. However the major difficulty with this one is centering the wheel. Most bikes you see aren't centered -- they're actually a couple mm off. Another major difficulty was was finding a offset front sprocket to get good chain clearance. Ended up welding two sprockets together. In hindsight I should've just measured and had a custom setup made. The rear 530 sprocket is from a 2001 GSXR 1000. It's important that I can do some canyon carving on her so I went a little overboard but very happy with the results. All-in-all I kind of should've went for a dual Ohlins setup... probably handles better... However I've heard somewhere that monoshocks get you laid.

The shock is from a 2006 Ducati 800 SuperSport -- the reason being I had wanted to install it as a diagonal/horizontal monoshock from the upper swingarm brace to the tank mount area. The Ducati has the same set-up as this. However, the machine shop I am working with was adamant that brace wouldn't be strong enough (I trust this guy -- he knows what he's talking about!). We ended up mounting down low, nearer to the axle, forcing a vertical setup and making the shock geometry a bit wonky. The stock Ohlins dual-rate spring was having issues so we swapped out to a heavy-duty spring. Works fine now.. I would say about 90% of the way there... she's now ridable with very good clearance.. however it probably could still use a bit of tinkering and fine-tuning. All in all I probably shouldn't have used this particular shock...

I've taken this is a very interesting learning experience and a crash course to shock geometry. The important point is to have the shock react at the angle it is originally intended to -- usually the shock wants to compress at a 90° angle relative to the bottom mount and overall swingarm movement. It's funny after all this I realize most of the mono builds featured on BikeEXIF are actually done incorrectly -- a lot of them aren't actually ridable bikes (too stiff or too soft).

Here's a photo of the shock mount. Its basically a series of gussets, about 2.5 inches down, connected to the stock horizontal brace/tank mount location. Originally we had created a mount directly to the tank mount -- however the bike ended up having about 3 inches clearance and mushy suspension travel. It functions well at the new location, albeit stiff.





Still missing a bit of frame strengthening in the area. I do plan to do some more hardcore riding on her so there is still a chance I will end up adding a linkage setup if I feel like she doesn't handle as well as I'd like. Unlikely, but worst case scenario will be utilizing the OEM GSXR 750 setup.