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Yamaha YDS3
Engine Rebuild
Engine Rebuild
Strip =
and
rebuild of a 1965 YDS3 engin=
e.
Within this presentation, you will=
find
details on
Within this presentation, you will fi=
nd
details on how to
correctly strip down a YDS3 engine. This is also valid for all of the vertically split =
crankcase Yamaha models such as the Y=
DS2, YDS3, YM1 and YDS5.
•
•Removing
the engine from the frame
•
1.First step as always is to drain the =
oil from
the bike whilst in the frame. Run the engine for 10 to 15 minutes if possible to warm the oil. The oil is =
drained
by loosening the 17mm drain bolt on the sump and also the 17mm drain bolt on the clutch casing.
=
2.Whilst the oil is draining, remove th=
e tank
and seat if not already done. Next is to fully loosen the carburettor rubber clamps and remove the rubbers
themselves.
3.Next, slacken the carburettors at the
manifold by using an 8mm socket on 250 and 305 models, do not use a screwdriver as this chews the finish =
on the
clamp bolts. Unscrew the carb tops and remove the slides from the <=
/span>bodies. I wrap these in bubble-wrap or
similar and tape to the top tube out of the road, this prevents the needles becoming bent or damaged.
=
;
4.Unscrew the exhaust nuts from the cyl=
inder
barrels and also the 2 nuts on the silencers. The silencers =
(mufflers) can remain on the bike on =
low pipe
models, high pipe models must be removed.
5.Next job is to remove the right hand =
engine
cover to gain access to the engine sprocket. This is held on by 5 <=
/span>No 3 Phillips screws.
6.Flatten the lock washer on the front =
sprocket
with a suitable drift. I use an air impact gun to remove the sprocket nut (32mm). You can also app=
ly the
rear brake and undo the nut against the chain tension. It is a standard thread. After removing the n=
ut and
the lock washer, split the chain and remove the sprocket.
7.Next is to remove the electrical wiri=
ng to
the generator assembly. There are 5 wires to remove as well as the =
green neutral light connection. The s=
tator
assembly is held on by 2 long screws. The points cam is also removed by undoing the 12 mm bolt and=
pulling
the cam out.
8.Undo the tachometer cable from the to=
p rear
of the engine and place along the frame top tube out of the way.
9.Remove the oil pump cover and disconn=
ect the
main oil feed to the pump. Pull this through the rubber grommet and plug the line with a 6mm bolt or =
screw.
Place at a higher level than the level in the tank. Also undo the oil pump actuating cable and stow along t=
he top
tube of the frame.
10.I always remove the cylinder heads and
barrels to make lifting the engine easier. Remember to disconnect the oil feed pipes to the cylinder inlets=
, these
have an 8mm head.
11.Remove the 4 engine bolts and the lef=
t hand
footrest, you are now ready to lift out the engine.
•
Stripdown
of the engine
•
First job is to remove the sump pan by turning the engine over on
itself. This is held on by 8 6mm No 3 Phillips headed screws. The <=
/span>shifter cam assembly is then taken off by removing the 4 screws in the c=
orners
of the assembly. This can then be gently levered out after the linkage is removed. This is=
done by
removing the 2 circlips and then the special washers and springs. Note the=
way
these come off.=
These
were not present on this engine as can be seen. A nut had been forced on o=
ne
side and the wrong circlip forced on the other.
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