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Understanding your carburetor and learning how to adjust it:
A. High-Speed Needle (HSN). The needle located on the
right side of the carburetor when viewing the boat
from behind.
B. Low-Speed Needle (LSN). The needle located on the
left side of the carburetor.
C. Idle Adjustment Needle. It is located near the top of
the carburetor.
D. Primer Bulb, located under the carburetor.
E. Choke lever, located on the front of the carburetor.
F. Fuel Inlet.
G. Fuel Return.
It is not necessary to change the needle settings if the
engine runs smoothly. Normally only the (A) high-speed
needle (A, HSN) will need adjustment from time to time
and only by a small amount.
Factory carburetor settings are:
A. HSN 1-1/4 turns from the closed position
B. LSN 2-1/2 turns from the closed position
If you run into problems tuning your engine settings, it is best
to re-set the needles to the above settings and start over.
IDLE STOP ADJUSTMENT
IMPORTANT: The idle adjustment needle (C) is set from
the factory to allow the boat to shut off when the throttle
trigger is pushed back. Do not adjust your idle using the
idle adjustment needle located on the motor. You must
use the throttle trim knob (#6, TH.TRIM) located on the
front of the transmitter to set the idle.
TROUBLESHOOTING
Problem:
The engine hesitates when accelerated rapidly.
The RPM increases at idling.
Solution:
Your (B) LSN is adjusted to lean. Open it up about 1/8th of
a turn and try again.
Problem:
The idle is not steady.
Solution:
Your (B) LSN is adjusted is too rich. Close it 1/8th of a turn
and try again.
Problem:
Engine stops at full throttle.
Engine sags when accelerated rapidly.
Engine sags with the boat at full speed
Solution:
Your (A) HSN is too lean. Open it up 1/16th of a turn and
try again.
Problem:
Your engine does not reach full RPM.
Carbon build-up appears consistently on your spark plug.
Solution:
Your (A) HSN is too rich. Turn it in 1/16th of a turn and
try again.
MAINTAINING THE RIO 51
When you are through operating your boat for the day,
be sure to perform these basic maintenance procedures.
This will prolong the life of the Rio 51 and help to ensure
trouble-free running.
ENGINE MAINTENANCE AND STORAGE
After a day of running, start your engine and choke it
while it is running to get a lot of fuel into the engine. Run
it for about 30 seconds, constantly choking the engine.
Afterwards it is a good idea to cover the inlet to the
carburetor to keep foreign materials out and moisture
from entering the motor.
For long term (winter) storage it is a good idea to flood the
engine as described above as well as coating the inside of
the engine with GrimRacer After Run Oil 8 oz (AQUB9551)
Before transporting your model, remove all of the gasoline
from the tank and lines and make sure your oil line shut
off clip is locked.
RADIO BOX MAINTENANCE
When finished running, open the radio box and leave the
radio box lid off overnight to allow any water to evaporate.
Should moisture gain access to the radio box, all
connections should be dried thoroughly. Hobbico
“Duster” Compressed Air (HCAR5500) will provide a blast
of air capable of blowing moisture out of connectors.
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