A working machine (10; 70; 90; 100; 120) comprising: an engine; engine speed controlling means for controlling a speed of the engine; a throttle lever; a throttle cable interconnecting the throttle lever and the engine speed controlling means for transmitting an amount of operation of the throttle lever to the engine speed controlling means, wherein the throttle cable has a proximal end connected to the throttle lever and a distal end connected to the engine speed controlling means; a plurality of guide members (55, 56) spaced from one another for guiding the throttle cable; a throttle cable clamping portion located between the guide members (55, 56) for pressing the throttle cable against the guide members (55, 56) so as to tighten the throttle cable; a pivotable arm portion having the throttle cable clamping portion; connecting means (64; 73; 101; 122) connected to the arm portion; and operating means (23; 25) connected to the connecting means (64; 73; 101; 122) and operable to move the throttle cable clamping portion between a tightening position to press the throttle cable clamping portion against the throttle cable for pressing the throttle cable against the guide members (55, 56) so as to tighten the throttle cable and a slackening position to slacken the throttle cable, wherein the operating means (23; 25) comprise a clutch lever and a shift lever for moving the throttle cable clamping portion to the tightening position when the clutch lever is switched to an operated position or when the shift lever is switched to a forward travel position, and for moving the throttle cable clamping portion to the slackening position when the clutch lever is switched to a non-operated position or when the shift lever is switched to a reverse travel position. an engine; engine speed controlling means for controlling a speed of the engine; a throttle lever; a throttle cable interconnecting the throttle lever and the engine speed controlling means for transmitting an amount of operation of the throttle lever to the engine speed controlling means, wherein the throttle cable has a proximal end connected to the throttle lever and a distal end connected to the engine speed controlling means; a plurality of guide members (55, 56) spaced from one another for guiding the throttle cable; a throttle cable clamping portion located between the guide members (55, 56) for pressing the throttle cable against the guide members (55, 56) so as to tighten the throttle cable; a pivotable arm portion having the throttle cable clamping portion; connecting means (64; 73; 101; 122) connected to the arm portion; and operating means (23; 25) connected to the connecting means (64; 73; 101; 122) and operable to move the throttle cable clamping portion between a tightening position to press the throttle cable clamping portion against the throttle cable for pressing the throttle cable against the guide members (55, 56) so as to tighten the throttle cable and a slackening position to slacken the throttle cable, wherein the operating means (23; 25) comprise a clutch lever and a shift lever for moving the throttle cable clamping portion to the tightening position when the clutch lever is switched to an operated position or when the shift lever is switched to a forward travel position, and for moving the throttle cable clamping portion to the slackening position when the clutch lever is switched to a non-operated position or when the shift lever is switched to a reverse travel position.