40 Years Strong: HONDA CB750F Custom by Tajima Engineering

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Tajima Engineering's CB750F

The first way to enjoy a Honda CB-F series bike, which were released from 1979 to 1983, is to maintain its performance through restoration and maintenance. Another is to customize it by changing the front and rear wheels to 17-inch and enhancing its dynamic performance, thereby achieving a modern ride while maintaining the original style. The latter requires dimensional changes and frame reinforcement, and the Tajima Special CB-F by Tajima Engineering is a prime example of this.

"The frame of a modern bike and the frame of a vintage bike may seem different, but what they are aiming for is much the same. The goal is to make sure that the tires can be used properly and that the engine power can be utilized. Over the past 40 years, tires have changed from bias to radial, and have gotten wider, so the stock bike itself has changed accordingly, and that change has been generally accepted. But in terms of design, you have your preferences. Even for the same CB, some people like the F but not the SF. So, we have been making customs for our customers that retain the F model design, but allow them to enjoy a modern riding style,” says Toshihisa Tajima, president of Tajima Engineering.

Just as above, the "Tajima Special" has the CB-F frame measured and modified, and then reinforced in 20 places to make it compatible with modern radial tires. In addition, using the specs of a modern CB (SC54) as a reference, the fork offset is changed and other dimensional modifications are made. The engine enhancements have also been established through experience working on many different bikes. The crankshaft is made lighter and fully balanced, and the metal journals that support it are mirror-finished. The head section is, as always, port machined and polished. The pistons are fluorine-coated with molybdenum disulfide to reduce friction in various parts, making the engine smooth and powerful.

And that's how we come to this CB750F. It is a Tajima RS-Spec Custom which boasts an appearance common to both the RCB, the bike that the CB-F has its roots in, and the RS1000, Honda's race-tuned version of the CB-F. After the basic 17-inch modifications mentioned above, an aluminum Y-shaped subframe was bolted on to connect the head pipe straight to the swingarm pivot. The RS1000 type exterior is then mounted on top of it. If you have the CB-F exterior, you can put it back on (remove the subframe and front cowl, and replace the rest) in 30 minutes, making this customization doubly sweet. This Tajima RS Spec CB-F, with its racer-like appearance, is designed to be enjoyed on the track, but at the same time it is flexible enough to be used for touring. It is also a custom that expands the range of enjoyment for the classic CB-F.

Handle

The front fork offset was changed from 45mm, the stock spec of the CB-F, to 35mm, the modern 17-inch standard. To achieve proper handling the amount of trail has also been changed from the CB750F's 117mm to 100mm, based on the CB1300SF (SC54) specs. The meter is STACK, and the front master cylinder is equipped with a NISSIN radial pump.

Bodyworks

The front cowl and inner brackets were made based on the RC30 (VFR750R) racer that Tajima raced in the Suzuka 8 Hours endurance race, and the two-light type headlights are also from the RC30. DZUS fasteners allow for easy installation and removal.

The aluminum tank is handmade by Tajima Engineering with a quick-charge cap common on endurance racers, and the RCB-style paint job was also done by Tajima. The Y-shaped part seen under the tank is an additional subframe of 38mm in diameter, which is bolt-on and made of 7N01 aluminum.

Engine

The base is a CB750FC, with the frame reinforced in 20 places. The engine is a CB1100R engine with the displacement kept at 1062cc, but with a lightweight crankshaft, enlarged ports, molybdenum disulfide coating and fluorine treatment on the pistons, and new bearings and metal parts. An FCR φ37mm carburetor was selected for the intake.

Chassis

Tajima's CB-Fs often uses stock suspension components to reduce the burden on the owner, keep the 780mm front fork length, and balance cost with performance. Here, the forks are 43mm diameter with KYB inner tubes (hard coated) and SHOWA outer tubes.

The swingarm is from another Honda model and was modified by Tajima. The wheels are 3.50-17/6.00-17 size, also from another model. The exhaust is the shop's original 4-1 exhaust.

Gallery

Specifications

Part	Details
Carb / Intake	KEIHIN FCR φ37mm Carburetor
Exhaust	TAJIMA ENGINEERING Original 4-1 Exhaust
Frame	TAJIMA ENGINEERING Original Subframe
Brake	NISSIN Radial Brake Master Cylinder 19mm Black/Buffed Clear brembo 4P Cast Monoblock Radial Mount Caliper
Suspension	WP Twin Shocks
Steps	CHASE MOTORCYCLE Rearsets
Drive System	EK Chain 530ZVX3 (CR;NP) Drive Chain
Handle / Steering	STACK ST200 Clubman Tachometer
Bodyworks	TAJIMA ENGINEERING Original FRP Cowl TAJIMA ENGINEERING Original Cowl Bracket TAJIMA ENGINEERING Handmade Aluminum Tank TAJIMA ENGINEERING Original Seat and Seat Cowl

Original Source of this Article

Heritage & Legends