Adjustment,Carburettor Cleanliness 12 - O.S. engine MAX-21XM Owner's Instruction Manual

ADJUSTMENT
WARNING :
Running the engine with the boat out of the water, with-
out load and without cooling water, will seriously damage
it, due to overheating. Therefore, always lower the boat
into the water immediately after the engine has been star-
ted, so as to prevent over-speeding and to allow cooling
water to be forced up to the cylinder-head. Having carried
out the initial running-in (''breaking-in'') procedure as de-
scribed before, complete the running-in as follows:
Open the throttle slightly from the
1.
idling position and start the engine,
following the procedure described
previously.
2. Lower the boat into the water,
gradually open the throttle and run
the boat straight ahead for 20 to 30 metres at full throttle.
Now return the model and close the needle-valve 20 to 30˚.
Repeat the run, taking note of the improvement in speed.
Continue with further runs, gradually closing the needle-
3.
valve (20 to 30˚at a time) until no further increase in speed
is obtained.
If the needle-valve is closed beyond the optimum setting,
4.
the model will slow down, accompanied by visibly
diminished exhaust smoke. In this case, immediately
throttle down and return the model to shore. Re-open the
needle-valve approximately one-half turn and repeat the
runs until the optimum needle setting is found.
5. Aim to have the model achieving its highest performance
after the engine has consumed about one litre of fuel.
Having found the optimum needle-valve setting, make a
note of the number of turns necessary to re-establish this
from the closed position.
6. With the engine run-in and the optimum needle-valve
setting determined, the mixture control valve should be
checked as follows:
Launch the boat and gradually open the throttle to its fullest
7.
extent. If at this point, the engine puffs out a good deal of
smoke and does not accelerate smoothly and rapidly, it is a
sign that the idling mixture is too rich.
Therefore, turn the mixture control screw clockwise 45 to
60˚. Repeat the run and recheck the result.
If, on the other hand, the idling mixture is too lean, the
8.
engine is likely to speed up momentarily, then cut out
1
Fig.-
abruptly when the throttle is re-opened. In this case, first
turn the mixture control screw counter-clockwise 90˚to
make sure that the mixture has become richer, then make
incremental adjustments, each way, until an acceptable
balance between rich v.lean settings is achieved. Carry out
these adjustments
conditions, until the engine responds quickly and positively
to throttle movements. Use a small screwdriver to adjust
the mixture control valve via its slotted screwhead in the
center of the outer end of the throttle rotor.
12
patiently under actual running