Husqvarna SMS4, Workshop Manual, Page: 55 / 136

F1.19 Part. N. 8000 H4704 (07-2010)
31
32
33
ENGINE OVERHAUL
(Intake) valve seat width C •
0.90-1.10 mm (0.0354-0.0433 in)
(Exhaust) valve seat width C •
0.90-1.10 mm (0.0354-0.0433 in)
VALVE sEAts CHECk
• The following procedure is applied to all the valves and valve
seat.
1. to delete:
• Scale deposits (from valve face and seat)
2. Check:
• Valve seat
Pittings/wear Replace cylinder head.
3. measure:
• C width seat of valve "a" (see fig. 31)
Not conforming to specifications Replace cylinder head.
a. Apply Prussian blue (Dykem) "b" on valve face. (see fig. 32)
b. Install the valve in the cylinder head.
c. Press the valve through the valve guide and on the valve seat
so as to leave a clear impression.
d. Measure valve seat width.
WARNING!
do not allow the lapping abrasive agent to pe- •
netrate in the gap between valve stem and valve
guide.
• Where the valve seat and valve face have touched, Prussian
blue is removed.
4. Lap:
• Valve face
• Valve seat
• After replacing the cylinder head or the valve and valve guide,
valve seat and valve face must be lapped.
a. Apply a coarse grain lapping abrasive agent
"a" to the face of the valve. (see fig. 33)
b. Apply molybdenum disulphide oil to the valve stem.
c. Install the valve in the cylinder head.
d. Rotate the valve until the valve face and the valve seat are evenly
lapped, then remove every trace of lapping abrasive agent.