FE350 ENGINE
Cylinder Head
Page 13-12 2001 Pioneer 900 Gasoline Vehicle Maintenance and Service Manual
13
BREATHER VALVE (REED VALVE)
General Information
The function of the breather is to create a vacuum in the crankcase which prevents oil from being forced out
of the engine through the piston rings, oil seals or gaskets.
The breather has a reed valve which limits the direction of air flow caused by the piston moving up and down.
Air can flow out of the crankcase, but the one-way reed valve blocks return flow. It thus maintains a vacuum
in the crankcase.
Oil laden air in the crankcase passes through the reed valve and expands into the rocker chamber. In the
rocker chamber most oil separates from the air and drains back to the crankcase. The air passes through a
tube and vents to the intake manifold.
Breather Valve (Reed Valve) Removal
1. Unscrew the mounting screw (1) and remove the back plate (2) and reed valve (3) (Figure 13-16, Page
13-12). See page 13-20 for Breather Valve Installation.
CYLINDER HEAD CLEANING AND INSPECTION
1. Clean the head with a non-flammable solvent and dry thoroughly.
2. Bead blast or scrape carbon deposits from head. When scraping carbon deposits, be careful to avoid
scratching or nicking the cylinder head.
3. Inspect the spark plug port threads for damage. If threads are damaged, replace the head.
4. Place the cylinder head on a surface plate (Figure 13-17, Page 13-12).
5. Measure the space between the surface plate and the head with a feeler gauge (1) to check the flat-
ness of the head surface (Figure 13-17, Page 13-12).
6. If the head is warped more than 0.002 inch (0.05 mm), replace the head. See following CAUTION.
∆ CAUTION
• Smooth out any damaged spots in the combustion chamber (1) using a small grinder. Sharp edges in
the combustion chamber may cause pre-ignition. Do not remove any more material than is necessary
or change the shape of the combustion chamber (Figure 13-18, Page 13-13).
• Do not grind the valve seats or the gasket surface.
Figure 13-16 Reed Valve
Figure 13-17 Check Flatness of Head Surface
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