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On the contrary, by increasing the altitude it is necessary to reduce the max. jet size by about 2-3 points for
every 350m altitude Increase.
The above data are only indicative, as many factors influence the carburetion and only a few among them
are ponderable. With these indications we wish to give the owner a general guide line and avoid damaging
the engine under variations of ambient conditions which make the carburetion substantially leaner.
A fine carb. adjustment will always have to be made according to the experience and to the tests performed
on the track.
As completion of this guide line, here are a few general recommendations: .
the carburettor is provided with an enrichment system for starting the engine
( "C" lever - see fig.5) when the engine is cold and/or when the
engine has been kept out of operation for a certain time. To get the max
efficiency this device must be used with gas throttle closed or slightly
opened. A few seconds after the engine has been started, shut the
enrichment to avoid system to avoid flooding the carburettor.
The real problems which could be experienced with these
carburettors are exclusively connected to the fuel feeding.
The fuel feeding is regulated by the floater-valve system located in the
float chamber.
• In case impurities (particles) are present in the fuel, these might prevent
the admission valve from properly closing; the level in the float chamber
will increase and the exceeding fuel is discharged through the carb.
breather. In this case, it is necessary to disassemble the chamber,
remove the floaters and the admission valve, then clean with
compressed air (see fig.6 - 7).
• In case of puncture of one or both floaters, the admission valve cannot be closed, and so the exceeding
fuel overflows through the breathers. In this case it is necessary to disassemble the float chamber, check
the fuel feeding into the floaters and replace them with others with same weight.
In case the engine has to remain out of operation for a long period, the fuel admission valve could get
stuck (either on opening or on closing position) due to presence of incrustations.
In the first case, the same fuel overflowing phenomenon from the carb. breathers is experienced, in the
second, the engine does not start for insufficient feeding.
It is therefore necessary to disassemble the float chamber, check if there is fuel inside, remove
incrustations and re-establish the proper fuel admission through the floater-valve assembly.
Fig.6
Fig.7
26
Fig.5
C
MAN-051 ING
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