Main Bearing Shell Selection - Yamaha TDM850 User Manual

2»52 Engine, clutch and transmission
"ftSSS
29.20 Measure the width of the crushed
Plastigauge (be sure to use the correct
scale - metric and imperial are included)
8 and 6 mm lower crankcase bolts and apply
new engine oil to their threads. Insert them (with
their washers where fitted) in their original
locations. Secure all bolts finger-tight at first, then
tighten them evenly and a little at a time in the
correct numerical sequence to the torque
settings specified at the beginning of the Chapter
(see illustrations 25.4a or b). Make sure that
the crankshaft is not rotated as the bolts are
tightened.
16 Turn the engine over. Clean the threads of
the 8 and 6 mm upper crankcase bolts and apply
new engine oil to their threads. Insert them (with
their washers where fitted) in their original
locations. Secure all bolts finger-tight at first,
then tighten them evenly and a little at a time in
the correct numerical sequence to the torque
settings specified at the beginning of the Chapter
(see illustrations 25.4a or b). Make sure that
the crankshaft is not rotated as the bolts are
tightened.
17 Unscrew the 6 mm and 8 mm upper
crankcase bolts evenly, a little at a time in a
reverse of the numerical sequence until they are
finger-tight, then remove them (see illustrations
25.4a or b) The number of each bolt is cast into
the crankcase. Note the copper washers fitted
with some of the bolts. Note: As each bolt is
removed, store it in its relative position, with its
washer where applicable, in
template of the
29.24 Main bearing housing numbers (arrowed)
crankcase halves. This will ensure all bolts are
installed in the correct location on reassembly.
18 Turn the engine upside down so that it rests
on the cylinder head studs.
19 Unscrew the 6 mm lower crankcase bolts,
the 8 mm bolts, and the 10 mm bolts evenly, a
little at a time in a reverse of the numerical
sequence until they are finger-tight, then remove
them (see illustrations 25.4a or b). The number
of each bolt is cast into the crankcase. Carefully
lift off the lower crankcase half, making sure the
Plastigauge is not disturbed.
20 Compare the
Plastigauge on each crankshaft journal to the
scale printed on the Plastigauge envelope to
obtain the main bearing oil clearance (see
illustration). Compare the reading to the
specifications at the beginning of the Chapter.
21 On completion carefully scrape away all
traces of the Plastigauge material from the
crankshaft journal and bearing shells; use a
fingernail or other object which is unlikely to
score them.
22 If the oil clearance falls into the specified
range, new bearing shells are not required
(provided they are in good condition). If the
clearance is beyond the service limit, refer to the
marks on the case and the marks on the
crankshaft and select new bearing shells (see
Steps 24 and 25). Install the new shells and
check the oil clearance once again (the new
shells may bring bearing clearance within the
specified range). Always renew all of the main
bearing shells at the same time.
23 If the clearance is still greater than the
service limit
Specifications (even with new shells), the
crankshaft journal is worn and the crankshaft
should be renewed.

Main bearing shell selection

24 New bearing shells for the main bearings
are supplied on a selected fit basis. Code
numbers stamped on various components are
used to identify the correct size bearings. The
crankshaft journai size numbers are stamped
on the outside of the crankshaft web on the
a cardboard
right-hand end (see illustration 28.21a). The
block of three numbers are for the main bearing
journals (the block of two numbers are for the
big-end bearing journals). The main bearing
housing numbers are stamped into the upper
crankcase half (see illustration). Note that if
there is only one number stamped into the
crankcase, it means that all the journals are the
same number. 25 A range of bearing shells is
available. To select the correct bearing for a
particular journal, subtract the main bearing
journal number (stamped on the crank web) from
width of the crushed
the main bearing housing number (stamped on
the crankcase). Compare the bearing number
calculated with the table below to find the colour
coding of the new bearings required. The bearing
shell colour code is marked on the side of the
shell (see illustration 28.22).
Number
1
2
3
4
5
6
7
Installation
26 Clean the backs of the bearing shells and
the bearing cut-outs in both crankcase halves. If
new shells are being fitted, ensure that all traces
of the protective grease are cleaned off using
paraffin (kerosene). Wipe dry the shells and
crankcase halves with a lint-free cloth. Make sure
listed in this Chapter's
all the oil passages and holes are clear, and blow
them through with compressed air if it is
available.
27 Press the bearing shells into their locations.
Make sure the tab on each shell engages in the
notch in the casing (see illustration 29.11).
Make sure the bearings are fitted in the correct
locations and take care not to touch any shell's
bearing surface with your fingers. Lubricate each
shell with clean engine oil (see illustration).
28 Lower the crankshaft into position in the
29.27 Generously lubricate all the bearing shells
Colour
Blue
Black
Brown
Green
Yellow
Pink
Red
toned by Stalker