Automatic Compression Release (Acr); Section 9. Inspection And Reconditioning - Kohler Courage SV470 Service Manual

Inspection and Reconditioning
This section covers the operation, inspection, and repair/reconditioning of major internal engine components.
The following components are not covered in this section. They are covered in sections of their own:
Air Cleaner, Section 4
Carburetor and External Governor, Section 5
Ignition, Charging and Electric Starter, Section 7
Clean all parts thoroughly. Only clean parts can be accurately inspected and gauged for wear or damage. There
are many commercially available cleaners that will quickly remove grease, oil, and grime from engine parts.
When such a cleaner is used, follow the manufacturer's instructions and safety precautions carefully. Use gasket
remover to remove old material from the valve cover, cylinder head, crankcase, and oil pan. Do not scrape the
gasket surfaces, as this could cause damage that results in leaks.
Make sure all traces of cleaning solvents are removed before the engine is reassembled and placed into operation.
Even small amounts of these cleaners can quickly break down the lubricating properties of engine oil.
Refer to A Guide to Engine Rebuilding (TP-2150) for additional information. Measurement Guide (TP-2159-A)
and Engine Inspection Data Record (TP-2435) are also available; use these to record inspection results.

Automatic Compression Release (ACR)

This engine is equipped with an Automatic
Compression Release (ACR) mechanism. The ACR
lowers compression at cranking speeds to make
starting easier.
Operation
The ACR mechanism consists of an actuating spring
located in the exhaust side cam gear. A thrust washer
and mounting of the closure plate hold the ACR in
position. See Figure 9-1. At cranking speeds (700 RPM
rounded surface of the control pin protrudes above
the exhaust cam lobe. This pushes the exhaust valve
ratio of about 2:1 during cranking.
than the cam lobe. The control pin no longer has any
full power.
Inspection and Reconditioning
Section 9
When the engine is stopped, the spring returns the
release position, ready for the next start.
Cam Gear
Thrust Washer
Figure 9-1. ACR Details.
Control Pin
Lower Section
Cam Lobe
Flyweight
Spring
Section 9
9
9.1