Function Test - Husqvarna HS 139A Workshop Manual

11. Remove the inlet valve and the exhaust valve. Make
notes of which one of the valves is the inlet valve
and which is the exhaust valve.
12. Assemble in the opposite sequence.
6.10.9 To clean and examine the cylinder valves
1. Disassemble the cylinder valves. Refer to
disassemble the cylinder valves on page 36 .
2. Clean the cylinder valves. Use a wire brush if it is
necessary.
3. Examine the valve heads for cracks. Use valve
compound to grind down small dents on the valve
heads.
4. Make sure that all parts of the cylinder valves are in
the tolerance intervals. Replace the cylinder valves if
they have too much wear. Replace the cylinder
block if the cylinder valve guides have too much
Standard dimensions and wear limits
wear. Refer to
on page 45 .
5. Grind the cylinder valves before you assemble them.
To grind the cylinder valves on page 37 .
Refer to
6.10.10 To grind the cylinder valves
1. Disassemble the cylinder valves. Refer to
disassemble the cylinder valves on page 36 .
2. Apply a thin layer of bearing paste on the valve
head.
3. Put the cylinder valves into the valve guides.
1425 - 001 - 03.06.2020
4. Turn the cylinder valves until you can see an
approximately 0.8 mm wide matt grey stripe around
the valve heads.
5. Remove all bearing paste and make sure that the
valves are clean before you assemble them.

6.11 Function test

6.11.1 To measure engine rpm
1. Start the engine.
2. Remove the engine cover.
3. Hold the tachometer against the spark plug cap.
4. Let the engine operate at idle speed to measure the
idle speed rpm.
To
5. Make sure that the idle speed rpm is correct. Refer
Technical data on page 41 . Adjust the idle speed
to
if it is necessary. Refer to
on page 27 .
To
6. Operate the engine at full throttle to measure the full
throttle rpm.
7. Make sure that the full throttle rpm is correct. Refer
Technical data on page 41 . Adjust the idle speed
to
if it is necessary. Refer to
on page 27 .
8. Install the engine cover.
6.11.2 To examine the valve play
1. Make sure that the engine is cold.
2. Remove the spark plug.
3. Remove the 4 screws on the cylinder head cover.
4. Remove the cylinder head cover.
5. Push the piston fully to the to dead center of the
compression stroke.
To adjust the idle speed
To adjust the idle speed
CAUTION: Make sure that the valves are
fully closed.
Repair instructions- 37