GENERGY 1500RPM SDE Serie Instrucciones De Uso página 67

The air inlet and outlet are made of different materials. The air intake, air outlet
and valve seat must match and be perfectly rectified to prevent air leaks.
When the valve or valve seat are burnt or damaged there are air leaks, a
rectification would be necessary. After the rectification, check the valve and
inspect the seat status to see the perfect adjustment.
The valve seat is made of a cast iron alloy. The normal width of the air valve
and the valve seat is: 1,2 - 1,6 mm. After long term use and various
rectifications, if the sealing surface is made wider, it will result in poor sealing, in
this case a reamer will be used to correct the positioning in the inner hole of the
air valve duct, and then, the valves and the inner hole position are rectified, as
required.
As new, the sinking distance between the plane of the air inlet and the air outlet
of the cylinder head is 0.7 to 0.9 mm as shown in Figure 5. After several
corrections, the sinking distance may increase. When it is more than 2 mm, it is
recommended to change the valve seat.
Fig. 5 Sinking valve
The space of the valve should be checked frequently. See Section 1 of Chapter
V for details on setting methods. If the valve clearance is excessive, this may
affect the accuracy of air distribution and timing, and increase noise of the
structure of the valve; insufficient space may lead to incomplete closure and
burning of the valve.
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