A) Basic setting Remove choke cover. Close choke butterfly by hand. Loosen bolt in pivot unit. Adjustment screw must point towards topmost notch of stepped disc. Fasten pivot unit to pull rod (3) with A = 1.5 mm (0.059 in) play between pull rod (1) and actuating disc (2). Then press clamping ring against pivot unit without play. |  |
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Adjusting screw must point towards topmost notch of stepped disc. Press pull rod (1) upwards and actuating disc (2) against pull rod(1). |  |
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Set choke butterfly opening¹ at butterfly wing facing downwards by means adjusting bolt (4). On carburetors with delayed pull down, remove paint mark or sealing compound and adjust choke butterfly opening¹ by turning bolt (5). After adjusting opening¹, secure bolt (5) by applying paint or sealing compound. If a carburetor with delayed pull down (6) does not operate smoothly after the engine has been started, it may be converted to the old version with valve cover (7). The following parts are required:
 ¹ See technical data
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B) Adjust preload at choke butterfly On carburetors with one coil spring (1) on the connecting rod and without a temperature switch in the intake pipe, the projection at the top of the starter until must be opposite the notch in the starter cover. Starter cover marked by yellow dot. Heater filament 20 ohm. |  |
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On carburetors without a coil spring on connecting rod (2) or with a temperature switch in the intake pipe, the projection at the top of the choke unit must be opposite the notch in the choke cover. Choke cover¹ marked by blue dot on the insulation block. Heater filament 20 Ohm; USA version 13 Ohm². Turn choke cover by 90º to the left to the lower projection on the choke unit only if the engine does not run porperly when starting in cold weather. ¹ black dot on USA version ² previously 20 Ohm |  |
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C) Electrical wiring diagram 1 = Choke unit with heater filament 2 = Temperature switch¹ for engine compartment (intake) air² ³ 2a = Temperature switch for coolant in front intake manifold 3 = Relay for automatic choke 4 = Plug connection 5 = Fuse 6 = Ignition / starter switch 7 = Thermostart`valve 8 = Idle shutoff valve Checking temperature switch 61 31 336. Checking relay for automatic choke 61 31 446 Checking Thermostart valve 13 11 059. ¹ opens above + 17º C (63º F) 3.3 L and Bavaria ² opens above + 45º C (113º F) 3.3 L and Bavaria ³ opens above + 17º C (63º F) - not 3.3 L and Bavaria 61 31 336 61 31 446 13 11 059
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D) Fast idling speed First make sure that the engine is at normal operating temperature, the air cleaner has been removed and the idle speed synchronized at 900 rev/min 13 11 009. a) In the case of distributors with advance and retard, pull off vacuum hose for retard (s). 13 11 009
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b) With engine switched off, detach connecting rod at rear. c) Lift up throttle linkage at rear carburetor by a few milimeters. Close choke butterfly by hand to an opening of 2.4 mm (0.095 in). - Check with twist drill shank at wing of choke butterfly facing downwards - This process shifts the stop lever in the automatic choke to the second stage. Release choke butterfly. |  |
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Start engine without accelerating. Idle speed must be 1400 rpm. d) Turn off engine to correct. Press accelerator linkage to full throttle position. Adjusting screw loosened - slower idle speed Tightened - faster idle spee 1 turn the adjusting speed equals about 300 rpm. |  |
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Repeat steps c and d until engine speed is 1400 rpm. Lift accelerator linkage several milimeters so that the adjusting screw can disengage itself on the stepped disc. Adjust the front carburettor in the same sequence. Attach connecting rod and move the automatic choke stop lever of both carburettors to 2. stage position. Release choke valves. Start engine without accelerating. The fast idle speed must now be 1800 to 2000 rpm. |  |
