1975 Honda CB750

Nick Hooper 1975 Honda CB750 SOHC

Engine and Electrical:

Engine: The original bike had over 50,000 miles so I rebuilt the top end of the engine. The crank shaft and connecting rod bearings/bolts were still in spec so I left them alone. Cylinders were in good shape so I just honed them out to keep the stock displacement instead of boring them.

Electrical: For the wiring I ditched the stock harness since it had been tampered with over the years and was in terrible condition. I installed a Motogadget M unit and Motoscope Mini and wired it from scratch. I also upgraded to Motogadget bar end turn signals and a custom LED tail light from Purpose Built Moto to keep all the lighting discrete and minimal. All control switches are also Motogadget to keep the handlebars very clean. The starter solenoid, voltage regulator and ignition coils are original or reproductions of the originals. The ignition lock is a Motogadget M Lok wireless key fob that’s activated by a sensor under the seat.

Battery: The battery is an Antigravity Lithium battery mounted sideways under the seat hump. The battery and electronics are mounted in custom trays and are almost completely invisible from the outside, which was part of my goal of building a very simple looking bike.

Headlight: The headlight is a 7 inch halogen from Motodemic and the mounting brackets I hand made from aluminum.

Oil Tank: I replaced the stock oil tank with an aftermarket one from Cognito Moto, which combined with the low profile electronics placement really cleans up the rear section of the bike. I also mounted an oil pressure gauge on the engine since I removed the stock oil pressure warning light.

Carburetors: The carbs are rebuilt to stock, with jetting adjusted to match the UNI air filters, which took place of the stock airbox for aesthetic reasons.

Exhaust: The exhaust is a fiberglass wrapped MAC 4:1 with a short aftermarket muffler. Oddly enough, one of the features on the bike that gets the most compliments is the low profile muffler, which is actually an off the shelf part from my local auto parts store, and only cost about $13.

Suspension, brakes and chassis

Forks and Front Brakes: The front end was swapped for GSX-R inverted forks and brakes adapted with custom billet aluminum triple clamps from Cognito Moto. The upgrade to the brakes is probably the most noticeable performance boost over the stock layout. Combined with aftermarket adjustable levers and steel braided brake lines, the GSX-R calipers remove that unsettling vague softness that the vintage caliper is known for.

Rear Brake: The rear brake remained the stock drum, but with a nice twist. The issue with the stock rear brake linkage is that the foot pedal would move with the swingarm which lead to uneven brake pressure depending on the contours of the road. So instead I fashioned a clutch cable and mounted it to pull on the drum instead of the solid linkage. So now the flexible cable applies even brake pressure no matter how much the swingarm moves, and the pedal never fights back.

Rear Shocks: The shocks are aftermarket 365mm (25mm longer than stock). The main reason for the longer shocks is to get the rear end higher for a more aggressive stance, and to ensure that the brake light doesn’t hit the rear tire.

Wheels and Tires: Before totally rebuilding the bike I took it on a few test rides and quickly realized that the stock tires left a lot to be desired. The rear tire would slide around a good bit under heavy braking and the bike never felt totally planted when leaned in a turn. So after taking my Ducati to a few track days I quickly realized the importance of high quality sticky rubber with a larger contact patch. So I installed custom 17” rims on the Honda, both much wider than stock. This allows me to run modern sportbike tires, currently Dunlop Sportmax. The front is a 120; rear is a 160. The smaller diameter of the rims helps the bike turn into corners easily, and the wide tires provide enough grip to carry through with confidence.

Chain and Sprockets: The wider rear tire did present a new challenge: The stock chain setup wouldn’t clear the rear wheel. So I offset both sprockets to compensate and everything moves freely. The old rusty chain has of course been replaced with a high quality O-ring chain.

Rearsets: The rearsets are custom from Cognito Moto. Other than looking great, they sit further back which really helps the riding position due to the absurdly low handlebars. The rearsets also offer a great deal of adjustability and can fold up for narrow garage parking.

Handlebars: One of the problems with the CB750 platform as a cafe racer is the height of the steering stem relative to the gas tank. To preserve the illusion of the flat line from the tank to the headlight I mounted fully adjustable clip-on style handlebars. The brackets are actually upside down so the handlebars sit lower than normal. Combined with the low-mounted headlight, this gives the bike a very nice body line that draws the eye straight across from the headlight back to the tail of the seat.

Seat: The seat is a custom piece from Tuffside. I chose the red diamond stitching to tie the rear section to the red stripe on the gas tank, giving the bike just enough accent color.

Frame: The frame is mostly stock, with most of the modification being removal of various mounting brackets and tabs, as well as adding the seat hoop of course, slightly angled upward to fit the seat. I also welded on the battery tray and bolted on the main electronics tray under the seat. The frame is powder coated in gloss black to endure many years of riding to come.

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