Modern China Motorcycles typically comprise
the following components: a frame; a rear wheel coupled to the frame via a rear
suspension assembly; a front wheel coupled to the frame via a front fork
incorporating a front suspension system; a handlebar rigidly coupled to the
front fork; a brake associated with each wheel; engine controls and a front
brake control mounted on the handlebar; a unitized engine and transmission
bolted to the frame; and a drive system coupling the transmission output to the
rear wheel.
As early China
Motorcycles were essentially modified bicycles, the frames were nothing
more than heavy-duty bicycle frames with an engine attached. Over the years,
frames were optimized for motorcycle
use and eventually incorporated suspension systems and greater rigidity for
safer handling. Most frames are constructed of welded-together steel tubing and
stamped heavy-gauge steel sheet metal. More exotic frames may be fabricated
from aluminum. Frames for lower-performance China Motorcycles and scooters may be
fabricated almost entirely of stamped steel sheet metal pieces that are welded
together to create a monocoque frame.
Many Honda touring China Motorcycles of the
1960s, such as the CA-150, CA-160, CA-72 and CA-77 had frames that were
fabricated from several large sheet-metal stampings that were welded together.
Although most China Motorcycles have what can be characterized as full-cradle
frames, in that a portion of the frame wraps beneath a unitized engine and
transmission unit, many China Motorcycles have been manufactured over the years
with spine, or backbone-type, frames where the engine and transmission unit
hangs from the frame. For some backbone frame designs, such as the Honda CA
series China
Motorcycles and many of the Honda CB series China Motorcycles of the 1960s,
such as the CB-160, the CB-72 and CB-77, and particularly the Honda racing China
Motorcycles of the 1960s, the engine and transmission unit formed a stressed
member of the backbone frame. China Motorcycles have also been manufactured
that had frames that were a combination of cradle and backbone. The Aerma cci
250 cc and 350 cc China Motorcycles built during the 1960s and 1970s had a
backbone frame built from tubing that incorporated a partial cradle that
extended forward from a lower portion of the backbone and supported the rear of
the engine and transmission unit.
The BiMoto/Benelli 250 cc 4-stroke-cycle China
Motorcycles had a backbone frame made from stamped sheet metal with a
similar partial cradle arrangement.
Both designs employed horizontal
single-cylinder engines. With such a layout, the axis of the crankshaft is
parallel that of the rear wheel, the cylinder is positioned in front of the
crankshaft, and the cylinder axis is horizontal, or nearly so. This engine
configuration is believed to provide optimal cooling for a single-cylinder
air-cooled engine.