Aeon AT56-69E, Service Manual, Page: 73 / 196

ENGINE
4-20
VALVE SPRING VERTICALITY
Service Limit: 1.6mm
NOTE: Replace seals whenever the cylinder head is
disassembled. Hardened, cracked or worn valve
seals will cause excessive oil consumption and
carbon buildup.
VALVE INSPECTION
1. Remove all carbon from valve with a soft wire wheel.
2. Check valve face for run out, pitting, and burnt spots. To
check for bent valve stems, mount valve in a drill or use “V”
blocks and a dial indicator.
3. Check end of valve stem for flaring, pitting, wear or damage
(A).
4. Inspect split keeper groove for wear or flaring of the keeper
seat area (B).
NOTE: The valves cannot be re-faced or end ground.
They must be replaced if worn, bent, or damaged.
5. Measure diameter of valve stem with a micrometer in three
places and in two different directions (six measurements total).
Replace if excessive wear is evident.
VALVE STEM OUTER-DIAMETER LIMITATION
Intake Valve Limit: 5.4mm
Exhaust Valve Limit: 5.4mm
6. Measure valve guide inside diameter at the top middle and
end of the guide using a small orifice gauge and a micrometer.
Measure in two directions, front to back and side to side.
CLEARANCE (STEM TO GUIDE) SERVICE
LIMITATION
Intake: 0.10mm
Exhaust: 0.10mm
7. Subtract valve stem measurement to obtain stem to guide
clearance.