KYMCO Downtown 350i Repair Manual page 209

4.Engine
Inspect the valves for damage and burning. Measure the valve stem diameter in
several places where the valve makes contact with the guide. If the measurement
is below specification replace the valve.
Item
Valve stem O.D.
Inspect the valve seat and the valve seat width. The valve seat should be
centered on the valve face. If the seat is pitted, worn out, or fits poorly on the
valve face the valve seat must be resurfaced.
Item
Valve seat width
Standard (mm)
IN 4.990 - 4.975
EX 4.970 - 4.955
Standard (mm)
IN
EX
4-35
Downtown 350i
1.2
1.2