Adjust the engine speed
Select AVE mode with the AVE/DYN selector switch. Put the RPM/VAC switch in the RPM position.
RPM selection is indicated by the LED below the RPM scale markings. Position the 2-stroke/4-stroke
selector according to engine type. The left scale ("CHANNEL 1") can now be used to monitor engine
speed from 500-2500 rpm with a scale resolution of 50 rpm per individual LED segment.
Adjust the engine speed to the rpm specified by the engine manufacturer for intake synchronisation.
Re-adjust to maintain the specified rpm if necessary during the synchronisation procedure. When the
synchronising task has been satisfactorily completed, return to the RPM mode to reset the engine
speed if necessary to the correct specified idling speed.
Synchronising
One of the carburettors is called the
"base" or "fixed" carburettor
, sometimes the
reference
carburettor.
This is the carb actuated directly by the throttle mechanism (cable or rod). It is best to
connect the rubber hose of channel 1 to this “fixed” carb for convenience in synchronising the others
to it. The other throttle valves are linked to the fixed carb. Study the linkage to understand in which
sequence synchronisation is possible without influencing previously set carburettors. See illustration
below left. There is one adjusting screw for each carburettor to be synchronised. See illustration
below right.
Usually you should start adjusting the carburettor next to the fixed one. The object is to achieve the
same reading on each of the channels during idling unless the values specified for a particular engine
are slightly different for specific cylinder-manifolds. (Some examples of such engines : 4-stroke
Mercury and Yamaha outboard motors, Honda’s VFR800 motorcycle engine). Start with the scale
range switch in the position 5-25 cm Hg. If necessary shift to the 20-40 cm Hg scale. The upper scale
range 35-55 cm Hg is only required for a very few motorcycle models. The scale selection is indicated
by the LED below the respective scale markings.
For some engines synchronisation to within 0,5 cm Hg is required, but for many engines, a
synchronisation to within 1 cm Hg is adequate, so always consult the service manual to check the
required degree of precision of the synchronisation before struggling to achieve a more precise result.
Flick over to the RPM display periodically while synchronising to check that the engine RPM has not
wandered off the setting, in which case readjust to the correct RPM before continuing.
In case of apparent difficulty in arriving at a satisfactory synchronisation even after several attempts,
for example if the LED displays indicate a synchronised engine but the engine sounds irregular,
select the
DYN
mode to check for and analyse defective engine seals. DYN mode selection is
indicated by the LED next to the “Pa” to the right side of channel 4 display. See §
8. DIAGNOSTICS
below. Refer also to the VacuumMate “3-in-1” wall poster for a quick reminder.
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