CLUTCH BATH
Correction for sticky clutch plates and difficult shifting.
The Guzzi single cylinder clutch is composed of a stacked
sandwich of 5 steel and 5 bronze plates. The steel plates are
connected in their center to the clutch fixed body hub on the primary
shaft of the transmission. The bronze plates are connected at
their perimeter to the gear-like outer body basket. There may
be one or two friction material rings installed at the base of this
stack as well. The outer body basket may run on a continuous
core bushing or it may have a packet of loose rollers. All of
these options depend on which model and year you have, but the
multi-plate design and basic operation are all the same.
Here
are pictures of a used plate stack and a fresh stack already
installed into my SuperAlce.
When the clutch is bound by its spring, the stack of plates and
all of the clutch components rotate as an intact, unit mass.
When you pull on the clutch handle, the spring pressure is countered
or relieved and the various pieces are released and allowed to move
independently. In theory, the stacked sandwich parts should all
slip smoothly over each other so that the outer body remains spinning
with the motor, while the inner body remains stationary. This
allows you to remain in gear with the engine running.
In
addition to these parts, there is a small passage at the top of the
crankcase which allows for a fine mist of air and engine oil to pass
from the crankcase chamber to the exterior clutch chamber.
(the
zip tie is in place just to demonstrate the oil passage route)
This mist of oil lubricates all the parts in the clutch
chamber, including the plates, and eventually condenses into a puddle
in the clutch chamber. It is a total loss system. There is no
way for this oil to get back into the engine case. Eventually,
this condensed puddle grows to the level that the bottom of the
clutch parts are sitting in a pool of oil and any further excess
starts to leak out behind the flywheel where the crankshaft passes
through the clutch chamber. There is no seal for this passage.
This blue tape represents the maximum depth of oil puddle within the
clutch chamber before it will simply pour out the crankshaft hole.
Guzzi didn't want to waste this oil mist, so there is also
a crossing passage which goes from the clutch chamber back to the
right side in the vicinity of the chain drive sprocket. Some of
the oil mist works its way out over here and drips onto the chain as
an automatic oiler. Clever, but messy. Many of us plug
that cross passage to reduce the mess and we then relay on modern
chain sprays. You can see my plug here.
Warm, thin, clean oil is a very nice substance to put onto the
clutch plates. It lubricates everything for smooth action and
minimizes wear.
However, cold, dirty oil acts more like a
glue than a lubricant and prevents free action of the plates.
The various clutch pieces all bind together and fail to slip as
intended. It can become very noisy to shift gears, especially
down into first gear. The noise also produces damage to the
tips of the gear teeth. The COMPLETE CURE is to fully
disassemble the entire clutch package and clean all the parts to new
condition.
The INTERMEDIATE MAINTENANCE solution is the BATHE
the clutch parts to remove any oil or dirt or wear material and
restore original action. Here is the procedure. It will be a
VERY messy job so protect your
floor and be prepared for
hazardous disposals.
First, at the lower rear curve of the
clutch cover plate, there will be a small, slotted screw-plug.
Remove that to drain away all of the condensed puddle of oil.
Here is the drain plug at the lower rear of the clutch cover.
Flipping the cover over, you may be able to see the interior
tip of this drain plug at the lower left.
Second, at the top of the left side crankcase you will find an
engine breather tube which returns crankcase pressure and oil mist
back to the oil reservoir tank. Adjacent to that breather tube
is a slotted plug which leads directly to the clutch chamber below.
(the
zip tie is in place just to demonstrate the oil passage route)
Third, introduce a pint of 'paint thinner' into the clutch
chamber via the upper plug. If you put too much, it will simply
run out the opening behind the flywheel.
CAUTION: In
America, 'paint thinner' is also known as mineral spirits. It
is a good solvent, but not particularly volatile or harsh to painted
surfaces. In Europe however, that term 'paint thinner' refers
to something Americans would call 'lacquer thinner'. This
latter material is highly flammable and an instant paint remover and
should NOT be used for this cleaning purpose. You might also
consider diesel fuel or Stoddard Solvent. Please don't use anything
substantially flammable and risk your moto and shop.
Fourth,
push the kickstarter repeatedly. While doing so, pull on the clutch
handle slightly so that the engine does not turn over but the
kickstarter does go through full throw. In this way, the
kickstarter will be rotating the inner body and steel plates, while
engine compression will be holding back the external body and bronze
plates. The paint thinner will remove oil, grime, and wear
contaminants from the clutch parts and drop them into the bottom of
the clutch chamber cover. Do this kicking and feathering for several
minutes.
Fifth, remove the plug at the rear lower corner of
the clutch cover and drain away the contaminated paint thinner.
Although dirty, it might be useful for other rough part washing tasks
around your shop. Let it settle for a week so you can decant
the liquid off of the settled sludge.
Sixth, repeat steps
three through five, perhaps a total of three rinse cycles.
Seventh,
clean up your mess and go for a ride. It will likely be several
months or a year before you need to repeat this procedure depending
on your miles driven.
As a TEMPORARY AID before you have an
opportunity to perform the more involved bathing or disassembly tasks
you can assist the releasing of the cold clutch plates. You
will generally find that shifting from neutral into second gear is a
lot easier than shifting down into first. So, on a cold started
motor, shift into second. Gently rev the motor slightly, and,
while holding the hand or foot brake, feather release the clutch
handle a few times so that you force a slippage of the plates several
times. Do this almost to the point of stalling the motor.
This will quickly heat the oil film which is binding the plates and
the underlying components. You may now be able to return to
idle and more quietly shift into first gear.
Patrick
Hayes
Fremont CA
mailto:STOPguzzihayes@gmail.com The mail link has some spam prevention. Please remove the “STOP” portion of text.