LONCIN LC2V80FD Maintenance Manual page 54

Chapter V Disassembly & Repair
Inlet
6.565~6.58 mm
valve
Exhaust
6.545~6.56 mm
valve
Replace the valve if the outer diameter of valve stem is less than the maintenance limit.
Inner diameter of valve guide
Remove the carbon deposition in the exhaust valve pipe with
reamer prior to measurement.
Measure and record the inner diameter of each valve guide.
Standard
6.6 ~6.615 mm
Clearance between valve guide and valve stem
Deduct the outer diameter of valve from the corresponding inner
diameter of valve guide.
Obtain the clearance between the valve guide and valve stem.
Standard
Inlet valve 0.02 ~ 0.05 mm
Exhaust valve 0.04 ~ 0.07 mm
If the clearance value between the valve stem and guide exceeds the maintenance limit, judge if replacing a new
guide of standard dimension will make the clearance achieve within the maintenance limit; if yes, replace the
valve guide (or cylinder head) as required and ream the valve guide to make it a better coordination. If the
clearance between the valve stem and new valve guide still exceeds the maintenance limit, replace the valve too.
Trim the valve seat again when replacing the valve guide.
Trim the valve seat
1. Thoroughly remove the carbon deposition in the combustor and
on the valve seat.
2. Coat a thin layer of blue lead power on the surface of the valve
or ink of marking pen which is easily to be erased.
3. Insert into the valve and press it for several times to make it tightly close to the valve seat. Assure not to rotate
the valve on the valve seat. Coating on the valve seat will show the de-concentric feature of valve or valve
6.438 mm
6.435 mm
Maintenance Limit
6.672 mm
Maintenance Limit
0.15 mm
0.17 mm
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