Structure for controlling operations of secondary air supply means and throttle opener in internal combustion engine for motorcycles

摘要

A motorcycle having an internal combustion engine mounted on a main frame and including suction and exhaust systems, an exhaust gas cleaning means adapted to supply secondary air to the exhaust system for cleaning an exhaust gas flowing therethrough, a carburetor provided in the suction system and provided with a throttle valve therein, and a throttle opener provided on the carburetor and adapted to open the throttle valve slightly while the internal combustion engine is decelerated. A secondary air supply passage is connected to the exhaust system, and a flow rate of the secondary air flowing through the passage is controlled by a secondary air control valve. When a vehicle speed of the motorcycle has decreased to a level not higher than a predetermined level, the secondary air control valve is closed to stop supplying the secondary air to the exhaust system, and the operation of the throttle opener is rendered ineffective simultaneously. This prevents the temperature of the exhaust gas from increasing. Accordingly, a change in the color, and the discoloring, of an outer surface of the exhaust system can be prevented. Also, a decrease in the effect of engine brake can be prevented effectively.