TAKING OFF THE CYLINDERS OF
A BIG GUZZI
This will be a step-by-step
guide to take your cylinders off and back on again. For this job
you will need the tools as listed:
- 5mm Allan head socket
- 8mm Allan head socket (80mm long)
- 10mm Allan head socket
- 10mm socket (M6)
- 13mm hex open end(M8)
- 17mm hex socket (M10)
- piston ring compressor
- torque wrench
Obviously it is necessary to remove the exhaust system and the
carburetors with the intake manifolds. Last preparation is the
removal of the oil line behind the cylinder.
We start with the left cylinder:
- Take off the valve head cover
- Remove both spark plugs
- Bring the piston in TDC, this is the
area, where both valves are closed and the ignition takes
place
To do this, turn the
engine either with the bolt in the alternator (clockwise from
the front) or turn the rear wheel in fifth gear (I personally
prefer the rear wheel, spares you work), first the outlet
valve moves down and up again, then the intake valve does the
same, outlet again and so on; after the intake valve has moved
and is closed (rocking lever is up again), you have TDC (if
you've turned the engine in the right direction J), it should
be possible to move the valves. I use a little screw driver in
the spark plug hole to feel when the piston is coming up
- Loosen the adjustment nuts of the
valves
- Take out the 10mm fixing bolts from
the rocking lever
- Take out the shafts with the rocking
levers (remember the position of the washers and springs)
- Take out the push rods, check if the
pins on the upper and lower ends are still tight in the rod,
if not replace
- Take out the four 17mm nuts which hold
down the rocking lever bracket
- Remove the rubber rings on the four
studs
- Take out the 10mm Allan head screw on
top of the head (mostly very tight)
- Take out the 17mm nuts below this
screw and the other at the spark plug
- Remove the cylinder head
- Remove the cylinder
- Remove the gasket and the two little
rubber rings on the upper and lower stud
Destruction is done, now there is time to do
something useful, at this point in time you can check some
things visually.
Take a look into the cylinder, are there
still signs of the honing to see, that's good, means the surface
can keep the oil for greasing. Clean the cylinder.
Is the piston OK, are the rings broken?
You can check if the valves in the
cylinder head close tightly by putting the cylinder head upside
down on the table and fill the combustion chamber with gas. In
the intake and outlet you can see, if there is moisture running
down the valves. Better don't use a lighter for this :o) .
You can clean up the combustion chamber with a rotating brass
brush for you drill machine.
Take the plungers/lifters out, check the
bottom side, which is running on the camshaft, if there is any
pitting. That is most likely and I recommend to change them,
otherwise it will destroy the camshaft.
You can't check the camshaft without
turning the engine, what I wouldn't recommend. If you take a
look into the holes, where the plungers were, you only see the
ground circle of the camshaft.
After you have taken off the piston rings
(carefully, perhaps you need them later on), cleaned the
surfaces from the old gaskets and the oil, you can mount the
rings. Mount the three new rings (if one breaks - they are not
out of rubber - you have as spare ones the old ones). There are
three rings, the lower one is the oil ring and the upper two the
compression rings. The middle one is not symmetrical, the little
groove has to show to the bottom, the upper compression ring is
symmetrical. Bring the rings in a position, where the openings
are showing in different directions, 120 degree difference would
be perfect. So you will have minimum bypass loss.
Now you can build up the engine again:
- Put the plungers back in place
- Put the foot gasket and the two little
rubber rings onto the clean surface (check if all holes are
free)
- Use the ring compression tool to
compress the rings
- Lubricate the cylinder a bit and push
it over the piston (you can see through the cylinder if it
fits)
- Put the head gasket in place (check if
all holes are free)
- Put the cylinder head on
- Push the four little rubber rings over
the studs and mount the rocking lever bracket
- Tight the bracket with the four 17mm
nuts a little bit
- Put the other nuts in place and use
the torque wrench to tight all six down in three steps (30, 40
and 43 Newtonmeter; I don't know how much that is in
...pounds) in zig-zag shape
- Close the hole at the upper end with
the 10mm Allan head (perhaps a new rubber ring?)
- Put the push rods into the holes
- Mount the rocking levers and tight the
10mm screws
- Adjust the valve clearance
- Fix the oil line behind the cylinders
- Close the valve cover
DONE (with the left cylinder)
Now you can do the same job on the right cylinder, first search
for the TDC for the right cylinder and start the same sequence.
If you have finished both cylinders and
reassembled your bike, you can go for a ride for some miles to
heat up the whole engine. After that leave it to cool down over
night. The next day you can check the torque of the nut by
removing the spark plugs, the valve cover and the rocking lever
bracket. In my opinion it is not really necessary to check the
torque after 600 miles again, but it is not absolutely wrong.
Adjust the valves and you are ready to go.
Eric Koch, 1999