Wellbrock-Honda CB 750 Four – Limited Edition

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Wellbrock-Honda CB 750 Four - Limited Edition

Limited Edition: Wellbrock-Honda CB 750 Four

Classic conversion of a Honda from 1972

Content of

With an inflated engine, powerful 90 hp on the rear wheel and great racing looks, this 1972 Honda CB 750 Four is worth every sin despite its ripe old age.

Open the fuel tap, close the gas, carefully dose the choke, press the button. Brammm, brammm, brammm – with a pithy sound, the four-cylinder spits its burnt mixture through the crisp, short exhaust roar. The open 4-in-2-in-1 system from the Ami country only seems to be attached to the Honda for optical reasons; it is hardly suitable for noise reduction. Pure intention, after all, oldies are allowed to roar as much as they can at relevant events. Like the “Bikers Classics” in Spa-Francorchamps / Belgium, where the souped-up CB 750 Four from 1972 celebrated its racing debut this year. “You don’t stand a chance with the Honda against younger bikes from the late 1970s, such as a Kawasaki Z 1000,” reveals owner Wolfgang Wellbrock. “The somewhat older machines have to stretch a lot if they want to pass.”

D.The North German Honda dealer (www.wellbrock.com) dug deep into its bag of tricks for this purpose. Instead of the standard 61-series pistons, he built a fat 67.5-millimeter model. With an unchanged stroke of 63.0 mm, this results in a displacement of 901 cm³ – a full 165 cm³ or over 22 percent more than the original drive with 736 cc. In addition, Wellbrock changed the timing and increased the compression to over 10: 1. “I won’t give you any more details,” he grins, “every tuner needs his little secret …”.

There is no secrecy with the base engine. The engine comes from the type “F2”, the last series of the 750 series from 1978. Thanks to larger intake ducts and a modified valve train, the engine already pushes several hp more than the older engines, which were specified with 67 hp.

In the Racing Honda, a crankshaft that has been slimmed down by 50 percent rotates, which means that the four-in-line engine turns up damn fast. A special ignition cuts the juice only at an impressive 9500 rpm. 90 HP should arrive at the rear wheel of the CB. Almost 100 horses on the crankshaft – pretty tight for a 40-year-old racing iron!

On the chassis side, the oldie driver upgraded his racer mainly with other wheels. At the front, instead of a 19-inch rim, there is an 18-inch wheel in a comparatively wide 2.5-inch format (series: 1.85 inches). A wider wheel is also used at the rear: 3.5 instead of 2.15 inches. This allows slippers in the dimensions 100/90 and 140/70. A pump from the legendary RC 30 racer works on the otherwise standard brake. After all, the braking performance should be in no way inferior to the hot sound.

Technical specifications


Slurp, snorkel, suck: the carburetors delight the ears and eyes.

drive 
Four-cylinder in-line engine, air-cooled, 2 valves / cylinder, 66 kW (90 PS) at 9500 rpm on the rear wheel *, torque: no details, 901 cm³, bore / stroke: 67.5 / 63.0 mm, compression: over 10 : 1, four Keihin round slide carburetors, Ø 31 mm, ignition: Dyno 2000, multi-disc oil bath clutch, claw-shifted five-speed gearbox

landing gear 
Double loop tubular steel frame, steering head angle: 63.5 degrees, caster: n / a, wheelbase: 1450 mm, conventional telescopic fork, inner fork tube diameter: 34 mm, rear stereo spring struts, front / rear spring travel: 143/85 mm

Wheels and brakes 
Wire-spoke wheels, size front / rear: 2.5 x 18 / 3.5 x 18, front tires: 100/90 V 18, rear: 140/70 V 18, tires: Bridgestone BT 45, 260 mm double disc brakes with single-piston Floating caliper at the front, 180 mm drum brake at the rear
Weight  221 kilograms (without gasoline)
price  around 20,000 euros

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