Engine; Testing Cylinder Compression - Bosch PB-650 Service Manual

PB-650
PB-750

8 ENGINE

(B)
(P)
(L)
(R)
(N)
(S)
(O)

8-1 Testing cylinder compression

(A)
(C)
(E)
(F)
(G)
(Q)
(M)
(A)
ENGINE
(D)
(H)
(J)
(K)
(P)
(O)
NOTE: Test the cylinder compression when engine
is cold.
1. Move ignition switch to STOP position.
2. Remove spark plug.
3. Install a compression gauge 91007 (A) in spark
plug hole as shown and pull starter several times to
stabilize reading.
4. If the pressure is lower than approx. 80% of stan-
dard compression pressure, check cylinder bore,
piston, and piston ring if worn-out. (Refer to "1-2
Technical data" for standard compression pressure.)
5. If the pressure is more than approx. 130% of
standard compression pressure, check cylinder
combustion chamber and exhaust port, piston
crown, and muffler for carbon deposits.
NOTE: Compression pressure varies with the
volume of compression gauge tip occupying the cyl-
inder combustion chamber. If the volume of the
gauge tip is considerably different from the one of
spark plug, it is recommended to measure and note
compression pressures of brand-new engines as
standard pressure in advance.
6. Remove compression gauge, then reinstall spark
plug and spark plug cap.
(A) Cylinder
(B) Cylinder cover
(C) Intake gasket
(D) Exhaust gasket
(E) Cylinder gasket
(F) Piston ring
(G) Piston
(H) Piston pin
(J ) Snap ring
(K) Needle bearing
(L) Circular washer
(M) Ball bearing
(N) Dowel pin
(O) Oil seal
(P) Crankcase
(Q) Crankshaft assembly
(R) Woodruff key
(S) Crankcase gasket
35