Subject: Understanding a 4-Speed Trans
Author: Keith Ruff
Date: Oct 24, 2002, 1:23 PM
Post ID: 1711266255
Was thumbing through my 70's vintage Chilton manual and came across the
trans. I was wondering how the trans actually operates, how it selects
the different gears. Pic shows an "assembled 4 speed transmission"
drawing. The "layshaft" which goes to the driveshaft, has 4 gears on it
and 2 arm looking things, one on each side of the 2 inside gears with
one gear outside of each arm. Then there is the "mainshaft" which also
has 4 gears on it that appears to mate directly with the 4 gears on the
layshaft. Next there is the shaft that goes to the clutch, the one that
the actuator arm pushes on in the center of the rear case (aka plunger)
that I just replaced the O-ring on - it came out with the throwout
bearing magnetically attached. The final shaft is attached to the gear
selector. What I don't understand is what happens to select the gear?
I see that the clutch handle pushes the plunger which then will
disengage the clutch, and the book says that the gear selector rotates
the other shaft which then selects a different gear, but I don't follow
that part. What is also confusing is that the 4 gears on the layshaft
and mainshaft are in perfect alignment, indicating that all gears are
turning at the same time, so how are the different gears selected.
Highly confused here.
Also, I am trying to understand why my idle drops when I pull in the
clutch. Andy said it still is doing this "slightly". I'll have to
compare it to the way it was before. I was hoping it would go away as
he had found the clutch hub to be dirty with some slight surface rust.
Andy buffed the hub with a wheel and lubed it. What else can be causing
RPM's to drop when pulling the clutch? I wonder if something was not
installed properly by the Guzzi dealer way back when. I do have the
newer style needle throwout bearing, just wonder if perhaps something is
missing to not get a good enough disengagement of the clutch and somehow
it is hanging up when warm.
Keith Ruff
71 Police Ambassador - NJ