VW Carburettor Hints

Early VW Carburettor Hints

The following workshop bulletins are reproduced from Volkswagen dealer information of the early 50s

WORKSHOP BULLETIN No. K/3 - 1950

CARBURETTOR - FUNDAMENTAL HINTS

November 1950

1. A correct ignition timing and a precise automatic advance and retard are the first requirements when adjusting the
    carburettor.
2. All adjustments must be made with the engine warmed up to its normal running temperature.
3. Every carburettor spits in winter and when the engine is cold, if adjusted to a lean mixture. Poor acceleration and a
    tendency of the engine to stall will be the result.
4. Fuels of a higher boiling point promote carburettor flat spot and cause a more or less appreciable dilution of the
    lubricating oil.
5. The troubles mentioned under (3) may also be caused by, too less an advanced ignition, faulty contact breaker points, too
    less a breaker point gap (correct: 094 mm - 0.15t'), and dirty spark plugs. Especially in winter, the prescribed adjustment of
    5° before T.D.C. is of great importance.
6. The present-day quality of fuels in some countries causes a dilution of the lubricating oil of cars mainly used in city traffic
    or over short distances. A dilution up to ten per cent is permissible. Ten per cent correspond to 1/4 ltr. (0.5 U.S. pints, 0.4
    Imp. pints fuel in an engine Oil filling of 2.5 ltr. (5.3.U.S. Pints, 4.4 Imp. pints the oil level is then approx. 20 mm (4/5")
    above the top mark on the oil level gauge. The increased oil level does not cause any engine trouble. If an excessive oil
    dilution due to the particular operating conditions of the vehicle, is noticed it is advisable to carry out oil changes at more
    frequent intervals, say after every 1000 - 1500 km (600 - 960 miles).
7. An unreasonable way of driving often leads to complaints about a high fuel consumption. The consumption should
    therefore be checked under normal driving practice and with a reliable fuel. Only a careful fuel consumption test can
    convince the customer that fuel system and engine are not at fault.

WORKSHOP BULLETIN No. K/4 - 1950

CARBURETTOR - FUNCTION AND ADJUSTMENT

November 1950

Idle System: The smaller pilot jet air bleed in the SOLEX Carburettor 26 VFIS produces a considerably richer idling and acceleration mixture. That is why the idling adjustment is a bit more difficult to be carried out. Contrary to the VW Carburettor and SOLEX Carburettor 26 VFIS it is in this case mostly sufficient to turn the volume control screw out by a quarter of a turn (90°). A further turning out causes a strongly sooting exhaust and sooted spark plugs which eventually leads to ignition failure.

Acceleration: The strength of the acceleration mixture remains unaltered, while the idling mixture can be adjusted by careful manipulation of the volume control screw.. If the throttle valve is further opened from the idling position, a rich acceleration mixture is drawn in as long as the throttle valve covers the acceleration passage.

Normal Metering System: When further opening the throttle valve, the enriching effect of the acceleration passage is reduced and fuel is drawn through the economical metering system for normal working conditions. The fuel-air mixture is drawn through the spraying well and the venturi into the mixing chamber. If the engine is still cold, this economical metering is liable to produce a temporary loss of acceleration and power.

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