CARBURATION

The carburetor is adjusted at the factory before delivering; do not not try to modify the carburetion if you do not know how.

A "full rich mixture" produces more vibrations and increases consumption.

With a "lean mixture" the engine is runs evenly but it thends to overh(usually there are "blanks" in the carburetion)  

After 10 minutes of working, the spark plug will start to get dirty with fuel waste. 

spark plug Colour

yellow/gray

hazel brown/light brown

brown/black

carburetion

lean

just right

rich

 

Diaphragm carburetor

In order to work properly, the diaphragms (pump and valves) must be kept wet by the fuel mixture, after a long resting without fuel or after several working hours the diaphragms may need to be replaced. In case of doubts please do get in touch with us. The replacement may be necessary every year, the use of old diaphragms leads to a an increasing leaning of the mixture and piston seizure. In some cases it may be necessary a seasonal carburetion setting, especially if you change of altitude, for such a setting please do turn to an expert.

idle too lean :

difficult start, while revving up the engine tends to stop

idle  too rich :

the engine abates while leaving it at idle for ten sec. and it revs up slowly,  excess of smoke.

 

VALBRO

CARBURATORE.jpg (15549 byte)Our carburetor is provided with a starter (Choke) for cold starting

 

Flip up switcher A in position 2 for starting, in position 1 for functioning.

You can set the carburetion at the desired revs. by the long black downward screw C. By turning it anticlockwise you rich the mixture, while the opposite you lean it. The basic setting is between 1 and 2.5 turns from the shut position. The C screw must be turned very gently, always verifying the cleanliness of the "passage" (the point where the nozzle of the idle enters the nozzle of the full, at about half revs.) in revving up. If the engine pops, you tighten it, if it abates you loosen it

The D screw sets the revs. at idle, by opening the butterfly valve. 

 

 

 

TILLOTSON

The basic setting of Tillotson carburator is :

2,5 rev on L screw (at left on picture) for the idle setting and  1 1/4 rev.  on H screw (at right on picture) per il regime di massimo.

La corretta carburazione si ottiene regolando queste viti in modo che la carburazione sia regolare anche a metà apertura della farfalla, quando tutte e due le viti lavorano insieme. 

La terza vite, conica, regola il livello del minimo.

 

 

 

 

 

 

float-type carburetor.

The basic carburetion is for sea-level flight, the altitude may compel you to adjust it.

height m

full revs. nozzle

needle notch

0 - 1000

75/65

3

1000 - 2000

70/62

2

above 2000

 

2

Minor adjustments for the steadiness of the idling can be done by the side screw on the carburetor.

 

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RUNNING-IN

You must run-in the engine before flying.

Do not rev up for five minutes while running-in.

The running-in is over after consuming 10 liters of gas.

The lifespan of your engine can double with a proper running-in, while with a bad one you may damage it since the very first hours of working.

In the first phase of the running-in the engine must be switched on and off following the cycles below:

engine 1° cycle 2° cycle next

on

off

2 minutes

2 minutes

5 minutes

5 minutes

10 minutes

5 minutes.

While on, the engine must be gently set at different revs, starting from the lowest up to the highest.

Repeated revvings are unsuitable, the clutch may be surcharged.

After each switching off, do carefully check all the mechanic parts, bolts and knots. 

After at least 30 minutes of work you can fly avoiding high revs. for too a long time.  


A heavy pilot requests more power to fly, in such a case is better to run the engine on the ground for at least 1 hour.

After the first 30 minutes of run, do check all the bolts, knots and screws, particularly those of the engine and the prop as well. Those of the engine (bolts and knots) must be checked every 5 hours of flight.

Engine overheating may occur while running-in, you can recognize it by a loss of power.

In this case is very dangerous to keep it on, it is better shutting off and let cooling, OR, AT LEAST SLOW DOWN BELOW 5000 RPM before applying more power

A loss of power may occur because a mixture too lean, following a wrong carburetor setting or dirty in the filter, do check for such possibilities before restarting the engine 

In case of overheating it is advisable to check the head screws to verify the seal of the motor head. Usually a loss of seal can be perceived by dull strokes at starting or by oil leakage, once the air conveyer is removed.