CARBURETOR ADJUSTMENT
(continued)
Step 5
– Now Adjust for maximum power at 7600 rpm +/- 100. If max rpm is less than
this, turn the H-needle 1/8 turn clockwise. (Parajet Supply RPM Tachometer as an
accessory, should you wish to make fine adjustments as described please contact us)
Caution!!
– Do not close the H - needle (turn clockwise) more than this – 1 and 1/8 turns
from seat - overheating from too lean a mixture will cause engine failure or even
complete seizure!! It may take some time to find the optimum setting and for the
engine to stabilize at high rpm. Carefully observe and judge the best setting of the H –
needle. It is safer to error 1/16 or 1/8 CCW and lose 100 to 200 rpm than to tune for
more power and higher.
Step 6
– Again engage full throttle and return to idle. Continue this until the optimum
high rpm and stable idle are reached.
Step 7
– The carburetor is pre-set at the factory before shipment and you should
remember that the H - needle should not be adjusted and set for maximum rpm. It is
best to find maximum rpm but set the H – needle a few hundred rpm below the peak, in
a range close to 7800rpm.
Note
– Proper carburetor settings can be noticed by inspecting spark plugs after every
hour of engine use. A properly adjusted carburetor will reveal spark plug ceramic colour
to change from white to a medium brown. A carburetor that is too rich will be black and
sooty. Also, numerous oil droplets will appear on the propeller. White or very, very light
brown colour reveals too lean a mixture and caution here is advised.
Also pay attention to the reduction belt tension. If the belt is too loose then engine
response may seem good but the engine could over-rev to 8300rpm or more. Be sure
belt tension is within recommended tolerance (see reduction belt tension adjustment in
this manual)
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