The following workshop bulletins are reproduced from Volkswagen dealer information of the early 50's.
WORKSHOP BULLETIN No. K/3 - 1950
CARBURETTOR - FUNDAMENTAL HINTS
A correct ignition timing and a precise automatic advance and retard are the first requirements when adjusting the carburettor.
All adjustments must be made with the engine warmed up to its normal running temperature.
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.
Fuels of a higher boiling point promote carburettor flat spot and cause a more or less appreciable dilution of the lubricating oil.
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 5o before T.D.C. is of great importance.
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).
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
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 (90o). 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.