Onan MicroLite 4000 Series User Manual

10-6
Valve Seat Surface Width
1. Clean the valve seat surface.
2. Use a vernier caliper to measure the valve seat
width (Figure 10-10). (See Section
3. Dimen-
sions and Clearances
for seat width allowable
limit.)
3. Apply red lead to the valve surface to check for
scratches or unevenness.
4. When the measurement is within the allowable
limit, check the seating ratio. If the ratio is less
than 70%, the valve seat needs to be reground.
5. If the measurement exceeds the allowable lim-
it, replace the valve and regrind the valve seat
(see
Regrinding Seat Surface on Page 10-6).
Regrinding Seat Surface
1. Grind the valve seat surface with a 45° cutter.
Use a cutter appropriate for the valve seat sur-
face and valve guide diameter (Figure 10-10).
WARNING
Always wear safety glasses
with side shields when grinding to prevent
severe eye damage.
2. Install the valve and check for contact between
the valve face and the valve seat with red lead.
(If the valve has been in use for a long time, the
seat tends to come in contact with the upper
side of the valve face.)
3. Cut and readjust the width using a 15
° cutter so
the valve seat width makes contact in the same
dimension as the valve face width.
4. Cut the valve seat surface again with a 45° cut-
ter and recheck the contact between the valve
and seat.
5. Repeat steps three and four until the correct
contact is achieved.
6. Lap the valve seat until the seated rate is more
than 70% of the total contact area.
7. Use a grinding compound to finish the seat sur-
face.
Valve stem guides or valve seats that are worn,
loose, cracked, or severely pitted should be re-
placed. The valve guide and seat have to be
pressed out of the cylinder head and replacement
parts must be pressed in. The replacement cylinder
head assembly includes the valve stems and seats.
1. VALVE SEAT CUTTER
2. 0.79 RAD. (45) CUTTER
3. CONTACT CHECK
4. 0.26 RAD. (15) CUTTER
5. 0.79 RAD. (45) CUTTER
6. CONTACT CHECK
a. IDENTICAL DIMENSIONS
b. SEAT SURFACE WIDTH
FIGURE 10-10. REGRINDING VALVE SEAT

Onan MicroLite 4000 Series Specifications

General

Fuel Type	Gasoline
Frequency	60 Hz
Rated AC Output	4000 Watts
AC Voltage	120V
Rated AC Amperage	33.3A
Engine Type	OHV
Starting Method	Electric
Noise Level	68 dB at 23 ft