MZ TS 150 - Timing diagram; Checking the ring grooves; Determining the timing

Fig. 68.
OT
UT
us
Es
I) 0
.4 0
AS
Timing diagram
TDC
BDC
Inlet
opms
Transfer port closes
Inlet closes
Transfer port opens
Outlet opcns
Outlct closes
Width of piston Wear value
ring groove
2.04 +0.02 mm 2.10 mm
Pisto9 rings whose vertical play is excessive fail to
ensure a gas-tight seal and produce a "whining" sound.
If the locking pins in the piston ring grooves have be-
come loose, the piston cannot be reused.
Fig.
70. Checking the ring grooves
As a makeshift a graduated disk
(360" protractor) can
For cleaning the piston ring grooves, a sharpened piece
be used which is available from any stationer's
shop
of piston ring should be used, because a scraper or
(teaching aid). The disk is reinforced for workship use
screw-driver might enlarge the groove.
by riveting a sheet metal disk on it.
Loose scale deposits on the piston head are removed
Clamp the cylinder before reading the values deter-
by means of a wire brush. The firmly adhering layer
mined with the help of a pointer.
is left on the piston head because it protects the piston
from an uncalled-for heat absorption.
The same applies to deposits on the ring section and
the piston skirt.
l
.. ,
Fig. 69. Determining the timing
If an old piston is reused, the piston rings must
be
checked that they are free to move in the pis-
t o n r i n g
g r o o v e
S. Special attention must be
paid to the top ring because it is exposed to the highest
temperatures. In the case of abnormally high operating
temperature due to wrong carburetter tuning or igni-
.tion timing, it may be distorted; this is indicated by
a corrugated contact surface.
Each ring must be placed in the same
groove (and not with the sides re-
1
vkrsed) in which it was located be-
I
fore removal and run in.
Fig.
71. Cleaning the ring grooves
Piston-ring gap
in new condition
0.2 mm
Wear value:
1.5 mm
If the piston-ring gap is too small, the ends will butt;
as a consequence of the increased friction the wear
rate will increase, too.
The view that by fitting a new set of piston rings the
performance of an engine that has run for a long pe-