Patent GB-1537344-A (GB)
Title: Fuel supply means for internal combustion engine
IPC: F02D37/02
Filed: 1976-05-14
Abstract: 1537344 Spray carburetters; treating IC engine charges; timing ignition YAMAHA HATSUDOKI KK 14 May 1976 [17 May 1975]  19960/76 Headings F1B and F1H The cylinder 2 of an I.C. engine is connected by intake passage 7 to a two-barrel carburetter which includes the following features:- Starting carburetter 13, comprising float chamber 22, nozzle 16 and plug valve 15 which has a hole 18 which is aligned with passage 14 when plug 15 is in its lowest position. Vacuum chamber 19a is connected to intake passage 7 by duct 20, through solenoid valve 21. The duct is closed during starting provided that the engine coolant temperature is less than 45C by the action of thermo switch 23. A time delay device opens duct 20 to suction, so that passage 14a is closed, after a pre-determined time, provided that the  coolant temperature is above 15C, as detected by thermo-switch 30. First acceleration pump 80 comprises a pump chamber 82 supplied from float chamber 34 and mechanically connected to throttle valve 11a, so that fuel is pumped to nozzle 86 near Venturi 43 in barrel 11. Second accelerating pump 90 consists of fuel chamber 92, also connected to nozzle 86 and float chamber 34, and suction chamber 91, connected to intake passage 7 through solenoid valve 96, by duct 59. Valve 96 is energized to open duct 59, when the coolant temperature is less than 60C, by thermo-switch 98. Suction is thus applied to chamber 91 and moves diaphragm 93 to fill chamber 92 with fuel. When the throttle valve is opened the suction diminishes and fuel is pumped to nozzle 86 by spring 93a. Pump 90 operates  after the supply of additional fuel from pump 80 has ceased. Ignition timing control. A centrifugal timing control device 51 is provided and a vacuumoperated device 52, which comprises two chambers 56 and 57 separated by diaphragm 54 which actuates push-rod 55 and is biased by a compression spring to move push-rod 55 to the left in Fig. 2, so that the timing is retarded compared with the timing for normal running. Chamber 57 is connected to intake passage 7 by duct 67 which includes device 60 which provides for unrestricted fluid-flow in a direction away from the chamber and for restricted flow into the chamber and also includes solenoid valve 61. When the valve is not energized, duct 62 is open to intake passage 7. Valve 61 is energized when the engine coolant temperature is below 60C and chamber 57 is then connected to atmosphere. Chamber 56 is connected to intake passage 7 through solenoid valve 58 when the valve is not energized and is connected to atmosphere when valve 58 is energized. Valve 58 is electrically connected to power source 26 through normally closed contacts 63a of relay 63, which is energized to open the contacts when pressure switch 65 closes because the pressure in intake passage 7 is above -500mm Hg and switch 66 is closed because the throttle valve 11a is closed. Valve 58 then moves to the open-to-atmosphere position and the ignition timing to the normal position. Exhaust gas recirculation through duct 100 is controlled by valve 101 which includes vacuum chamber 104 connected by duct 105 to a port slightly upstream of throttle valve 11a, so that the amount of recirculated gas is in accordance with engine load. Dimensions of slow-running circuit. To improve fuel atomization the following ratios should exist between the diameter D of intake passage 11, the diameter d of passage 47 and the diameter do of air bleed 49:- d o /D = 0À035 to 0À065 and d/D = 0À35 to 0À100.