A. C4 Crankcase Principles
Shindaiwa C4 engine technology relies on a
sealed crankcase, just like a two-stroke. That
means air leaks can lead to serious operational
problems, just like they do in two-strokes.
In addition to the usual two-stroke sealing sites
(crankcase, spark plug and external bearing
seals), the four-stroke T2500 engine has these
additional sealing points:
Cam gear cover
Rocker arm cover
Sealed bearings
For proper engine operation, all these points
must be properly sealed.
Always install new cam gear and rocker arm
cover gaskets whenever covers are removed.
Never use cracked or damaged gaskets!
If new gaskets are not available, old
undamaged gaskets can be used if coated with
threeBond #1207-C sealant upon reassembly.
B. Pressure Testing Crankcase
Test sequence is similar to two-stroke pressure
test. Requires crankcase pressure testing kit:
P/N 72174-99200.
STEP 1.
Remove carburetor, but leave
insulator block/reed valve in position.
STEP 2.
Remove muffler.
STEP 3.
Install intake reed test plate.
STEP 4.
Install exhaust test plate.
STEP 5.
Check spark plug for proper torque.
STEP 6.
Install pressure gauge.
STEP 7.
Pressurize to 4-6 PSI. Pressure loss
should not exceed 1 PSI in 60 seconds. If
loss exceeds this figure, proceed to Step 8.
STEP 8.
Check common pressure-leak areas
first. They are:
Spark plug and plug sealing washer
Crankcase seals
Gasket areas
IMPORTANT!
Pressure
Testing
Crankcase
Crankcase & Intake Sealing
Section
7
Crankcase
Sealing
Principles
14
To pressure-test, mount block-off plates to
intake and exhaust ports and apply 6-8 PSI to
crankcase. Pressure loss should not exceed 1
PSI per 60 seconds.
The spark plug is a common area for leakage
during a pressure test. Always test with a new
plug installed.
Edition 2 • 09/2007
