Abstract: In forming a fuel inlet pipe FP, (1) a portion of a base pipe is expanded by use of an expander punch to form a processed pipe comprising a neck portion, of which the diameter is the same as that of the base pipe, a tapering portion, and an expanded portion, all of these portions being connected in coaxial relation to one another (coaxially expanding process); and (2) a central axis of the neck portion and a central axis of the expanded portion are decentered relative to each other, and the expanded portion of the processed pipe is further expanded by use of an expander punch having a diameter larger than that of the expander punch used in the coaxially expanding process, thereby forming the fuel inlet pipe FP (eccentrically expanding process). The coaxially expanding process is performed one time or a plurality of times, while the eccentrically expanding process is performed only one time.

Abstract: A fuel inlet comprises an inlet pipe, a breather tube, a retainer, a spiral groove, and the like. The inlet pipe is formed by processing a metal pipe and has an expanded portion, a taper portion, and a main body in the order from the fuel port. The expanded portion is formed by increasing the diameter by bulging. In order to prevent defects in the pipe such as cracks from being caused during bulging, SUS304, SUS304L, or SUS436 according to JIS is used as the material of the pipe. The diameter of the main body is 25.4 mm and the diameter of the expanded portion is 50 mm. A spiral groove on which a screw-type fuel port cap can be screwed is formed in the vicinity of the open end of the expanded portion, by crimping the inlet pipe and the retainer together. On the outer surface of the expanded portion in the vicinity of the open end is provided an outer-cylinder-like flange formed integrally with the inlet pipe.

Abstract: There is disclosed a muffler structure in which a valve opened/closed in accordance with exhaust gas pressure in a pipe is prevented from chattering by an inlet pipe provided with a first side hole and an outlet pipe provided with a second side hole with a valve biased by a spring to simultaneously close both the first and second side holes when the pressure is relatively low. When the pressure of the exhaust gas is relatively high, the pressure exerted on the valve by the exhaust gas in the inlet pipe is sufficient to open the valve and the exhaust gas introduced to the inlet pipe flows out to a second chamber via the first side hole, flows into the outlet pipe via the second side hole, and is exhausted to the outside of the muffler via the downstream outlet opening.

Abstract: The intake manifold includes a mounting flange formed as a forged or cast member and having a fuel injection valve-mounting portion provided on the mounting flange. Branch pipes are formed from iron series-containing pipe members, and are joined to the mounting flange. A plurality of mounting bosses can also be formed on the mounting flange to support a stiffener connected to a surge tank.

Abstract: In a muffler for internal combustion engine which is provided with a valve capable of closing and opening an open end of by-pass inner pipe, the opening and closing operation of the valve is performed via the exhaust gas pressure, without being affected by external factors. Also, the structure is simple and easy to be assembled. On a fixed shaft (36) supported in the vicinity of an open end (28a) of a by-pass inner pipe (28) is a valve (32) rotatably mounted. The valve (32) is urged against the open end (28a) by a coil spring (42), and when fitted in a flange part (38), it closes the open end (28a). When the revolving speed of the internal combustion engine is low, the pressure inside the by-pass inner pipe (28) is smaller than the operative force which is an addition of the urging force by the coil spring (42) and the external pressure. The open end (28a) is therefore closed.

Abstract: In a muffler for an internal combustion engine which is provided with a valve capable of closing and opening an open end of a by-pass inner pipe, the opening and closing operation of the valve is performed by means of the exhaust gas pressure, without being affected by external factors. Also, the structure is simple and easy to be assembled. On a fixed shaft (36) supported proximate an open end (28a) of a by-pass inner pipe (28) is a valve (32), rotatably mounted. The valve (32) is urged against the open end (28a) by a coil spring (42), and when fitted in a flange part (38), it closes the open end (28a). When the revolving speed of internal combustion engine is low, the pressure inside the by-pass inner pipe (28) is smaller than the operative force which is an addition of the urging force by the coil spring (42) and the external pressure. The open end (28a) is therefore closed.