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reprinted from the May 1983 issue of Cycle Magazine     

 

passages are more easily and reliably drilled, and jets fitted at the ends of the passages can regulate flow to the specified level.

To keep the Tempter's pistons flat (thus reducing heat transfer into the piston's crown) and to maximize combustion efficiency, Suzuki designers incorporated the Twin Dome Combustion Chamber shape which first appeared on the 1981 GS650. This

 

upstream of the valve head. (The Yamaha system stores excess fuel/air charges in small plenum chambers not connected to the carburetors.) At the opposite side of the air jet's orifice, the port's roof is quite flat and its area necked down considerably less than at the carburetor flange. According to Suzuki, this shape, determined by computer analysis, produces the flattest power curve practical and concentrates

 

most engines come alive - when cams and carburetors and ports and pipes harmonize to produce a burst of power - the GR just fades away. Suzuki designers have forsaken high-speed power for broad-spectrum tractability. Speed buffs won't like Suzuki's approach, but those whose riding demands down-low pulling power at sedate engine speeds will.

Considering the 650's overall middle-

configuration gives a very compact fuel-burning area. The GR650's slightly domed 77mm pistons rise only a couple of millimeters, yet yield an 8.7:1 compression ratio.

To further improve combustion at lean air/fuel mixtures, Suzuki engineers used an air-swirl induction system that draws air from the oval-venturi carburetors and delivers a jet-charge just 

power at the bottom end of the rpm scale.

Suzuki engineers certainly delivered on that objective. The GR's torque peak occurs at a low, low 3500 rpm. It remains virtually flat, generating 29 to 31 pounds-feet all the way to 7000 rpm, where the engine's peak horsepower occurs. As revs build, the engine accelerates hard, and at the point when

road character, the shape of the power curve is a fair trade. In the real road of street tooting, the rider can lug the engine down to an idle and the GR will accelerate willingly. A small amount of driveline snatch occurs up to 1500-2000 rpm, depending on the load. It's unnecessary to touch the 8500-rpm redline, and short-shifting at 7000 keeps the engine in it's most useful power

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