Honda HHT25S Manual page 25

SERVICE INFORMATION
SPARK TEST

Gasoline is highly flammable and explosive. If ignited,
gasoline can burn you severely.
Before testing the spark plug:
• Be sure there is no spilled fuel near the engine.
• Place the spark plug away from the spark plug hole.
1. Loosen the 5 x 12 mm screw and remove the top cover.
2. Drain the fuel tank or remove the fuel filter from the fuel tank
and drain the gasoline by pressing the carburetor primer bulb.
3. Remove the top cover and the spark plug.
Unburned gasoline can ignite if it is left in the cylinder. Pull the
recoil starter several times to release the unburned gasoline
from the cylinder before testing. Do not touch the flywheel fins
when pulling the recoil starter.
4. Install the removed spark plug on the spark plug cap.
5. Ground the negative (–) electrode of the spark plug to the
engine block.
6. Pull the recoil starter to check for sparks.
COMPRESSION TEST
1. Loosen the 5 x 12 mm screw and remove the top cover.
2. Drain the fuel tank.
3. Drain the gasoline by pressing the carburetor primer bulb.
4. Remove the spark plug cap and spark plug, and install a
compression gauge in the spark plug hole.
5. Open the throttle wide open and make sure the choke is open.
6. Pull the recoil starter several times with force and measure the
cylinder compression. Do not touch the flywheel when pulling
the recoil starter.
Cylinder
0.9 ± 0.15 MPa (9.7 ± 1.5 kgf/cm²,
compression
138 ± 22 psi)
@ 2,000 rpm*
* Decompressor mechanism engaged
2-14
WARNING
HHT25S•HHT35S
SPARK PLUG
COMPRESSION GAUGE
(Commercially available)