Specifications

46
Chapter 1 Engine, clutch and gearbox
39 Refitting the piston, cylinder barrel, cylinder head and
rocker arms
1 Raise the connecting rod to its highest point and pad the
mouth of the crankcase with clean rag as a precaution against
displaced parts falling in.
2 The piston is marked 'IN' denoting the inlet valve cutaway,
and must be fitted in the correct relative position ie, towards the
rear.
3 Lightly oil and fit the piston onto the connecting rod by
inserting the gudgeon pin. Replace the circlips that retain the
gudgeon pin, making doubly sure that they are correctly seated
in their grooves and that the circlip gap does not coincide with
the slot in the piston. Always renew the circlips as it is false
economy to re-use the originals.
4 Trim off any excess crankcase gasket from the cylinder
mounting face with a sharp knife. Refit the locating dowel to
each of the left-hand studs and install a new cylinder base
gasket, using a smear of grease to stick it in place. Ensure that
the cam followers have been correctly refitted on their shaft.
5 When fitting the piston rings first fit the oil scraper ring
centre section, ensuring that its ends butt together, then fit the
side rails on each side of it; these are fitted with their top
surfaces (identified by etched markings) upwards and with their
end gaps spaced 20 - 30 mm on each side of the centre section
gap. Of the two compression rings, the second is identified by
its tapered outer edge (the top ring being rectangular in section)
and the top surface of both is identified by the letter T, R or N
etched near the gap. Fit the compression rings with their top
surfaces upwards, each in its correct groove and with their end
gaps at 1 20° to that of the oil scraper ring. Lightly oil the piston
and the cylinder bore, place the barrel over the studs and lower
it onto the piston, compressing each ring in turn by hand to feed
them into the bore.
6 When all three piston rings are in the bore, the padding in
the crankcase can be removed and the cylinder barrel located
on the two dowels and secured with two bolts at the left-hand
side. Check that the cam followers are correctly located either
side of the cam lobe as the cylinder barrel is lowered into posi-
tion and be careful not to scratch their feet on the cam gear
teeth.
7 Note the position of the three dowels, (see photograph)
which should be positioned over three of the four studs. The
front right-hand stud does not have a dowel. A new cylinder
head gasket can now be placed in position, plus a new 0 ring
around the right-hand rear dowel. The cylinder head can now be
lowered over the holding down studs, and the pointed bolt fitted
and screwed lightly into the head of the cam follower pivot
shaft. Fit the two pushrods, ensuring that they seat in the cam
follower cups. The pushrod guide plate can now be fitted and
retained by two of the four cylinder head sleeve bolts.
8 Fit the remaining two sleeve bolts to the cylinder head, then
tighten all four bolts evenly and diagonally, finally tightening
them to 2.3 - 2.8 kgf m (16.5 - 20 Ibf ft). Tighten the special
bolt which screws into the cam follower pivot to 1.8 - 2.3 kgf m
(13- 16.5 Ibf ft). Slacken off the valve rocker adjusters, and fit
the rocker assembly to the cylinder head, tightening the
retaining bolts. Ensure that the pushrods engage in the rocker
cups.
9 Turn the engine over to align the T mark on the generator
rotor with the index mark on the crankcase, and set the valve
clearances to 0-08 mm (0-003 in) using a feeler gauge. Tighten
the locknuts, then recheck the clearances. Examine the rubber
seal in the cylinder head cover for signs of cracking or scuffing,
and renew if it at all suspect. Before fitting the cover, liberally
lubricate the rocker assembly with engine oil, and prime the
circular oil feed passage. Place the cover in position, and fit the
retaining screws, tightening them evenly.
39.2 Cutout for inlet valve is marked appropriately
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39.3 Refit the piston using new circlips 39.5 Feed piston into bore, then lower barrel into position