|
I've had this transmission apart twice now, it's taken a while
for me to get a full understanding of what's going on here for each
gear. I took a picture of every gear so I could see exactly what's
happening in every gear and neutral. I also discovered why
neutral-1st shifts are so hard on the transmission. Here's my
explanation of things:
First off, the microfiche exploded diagram is really helpful in seeing some of the
details.
Short summary: There are two sets of shafts with gears
that are all in constant contact with their countershaft companion.
The shaft seen in these pictures is the "Countershaft" or "Drive
Axle shaft", this contains the "gears". The shaft just below them is
the "Main shaft" or "Axle shaft", this contains the "pinions". Some
of the gears and pinions are connected to the shaft so that they are
locked to the shafts rotation, others are allowed to spin freely on
the shaft. Located on a rod just above the gears are three shift
forks (note: they are numbered right-to-left, 1-3). Connected to
"Shift Cam Drum", these forks move two of the gears (4th and 5th)
and one of the pinions (2nd/3rd) into different positions on the
shaft. This moving gears and pinion are what cause your transmission
to shift gears. This design also enforces sequential shifting. Take
a good look at the drum to see how the grooves impact the fork
positions.
The "Forked Gears":
These gears make it all happen, here's how: 4th gear, 5th gear
and the 2nd gear pinion have "Dogs", pertruding parts that engage
with their neighbor gears' or pinions' "slots". These three are only
parts fixed to their shaft, with the exception of the 1st gear
pinion, which is actually built into the shaft. By connecting with
these dogs/slots, they can transfer power to or from the other
freespooling gears to the shafts.
4th "Forked" gear: This gear has three positions, the left
position engages with 1st gear, the right position is engaged with
3rd gear and the middle position is not engaged.
5th "Forked" gear: This gear has two positions, the left
position engages with 2nd gear and the right position is not
engaged.
2nd/3rd "Forked" pinion: You can't see it in this picture,
but it's connected to the #2 (middle) fork. It has 3 positions. The
left position engages with the 4th gear pinion, the right position
engages with the 5th gear pinion and the middle position is not
engaged.
The Gears:
Listed from left to right in the
pictures:
Middle Drive Gear: This gear is fixed to the countershaft
and transfers power to the wheels. Whenever the countershaft and
this gear are moving, the wheels are moving.
1st Gear: 1st Gear freespools on the countershaft and is
always connected to a fixed pinion on the main shaft. When the
engine is running and clutch is engaged, this gear is ALWAYS moving.
It has slots for 4th gear dogs to engage with. Since 4th gear is
fixed to the shaft, then this causes the shaft to turn.
4th Gear: 4th Gear is fixed to the shaft, but can slide
into three positions. The 4th gear pinion free spools on the main
shaft. When 4th Gear is engaged, it is in the middle position and
the 2nd/3rd gear pinion engages with the 4th gear pinion, to
transfer power from the mainshaft through the pinion to 4th
gear.
3rd Gear: 3rd gear freespools on the countershaft. It's
pinion is fused to 2nd gear pinion, as described above. When the
engine is running and clutch is engaged, 3rd gear is ALWAYS moving.
When in 3rd gear, the 4th gear is engaged with it to transfer the
power to the countershaft. In this case, the 2nd/3rd pinion is in
the middle position.
2th Gear: 2nd gear freespools on the countershaft. It's
pinion is fused to 3rd gear pinion. When the engine is running and
clutch is engaged, 2nd gear is ALWAYS moving. When in 2nd gear, 5th
gear engages with it to transfer power to the shaft. Notice that
now, 4th gear sits as it does when in neutral, connected to it's
freespooling pinion.
NOTE: The infamous 2nd gear
problem is due to a poor contact area between the dogs on 5th
and slots on 2nd. In these pictures, the culprit washer has been
moved to the left side of 2nd gear, allowing better contact of the
dogs and slots.
5th Gear: 5th Gear is fixed to the shaft, its pinion is
freespooling. When in 5th gear, the 2nd/3rd pinion engages with the
5th gear pinion to transfer power to the pinion and then to the
gear.
Additional Info:
About Neutral and the Neutral-1st gear
shift:
In addition to the popular 2nd gear problem, there
has also been a number of 1st gear problems with this transmission.
The cause is due to how the gears behave when in neutral, and how
that effects the shift into first.
When the engine is running
and clutch is engaged, and the transmission is in neutral, 1st, 2nd
and 3rd gears are freespooling, but their pinions are fixed. Thus,
each of these gears is spinning on the countershaft, though the
countershaft is not spinning at all (remember, the countershaft and
wheel have a hard connection, if the wheel is stopped, the
countershaft is stopped).
Since 1st gear is so large, it has a
lot of momentum, disengaging the clutch and shifting into first
causes the non-spinning 4th gear to engage with the spinning 1st
gear. This causes the shifts to be hard. This is why there is a loud
"thunk" when shifting into 1st from neutral. To make it worse, the
bike is shaft driven; on chain and belted bikes, the chain or belt
will bounce to absorb some of the shock.
The way to avoid this
is to wait several seconds after releasing the clutch to engage 1st
gear. This will allow the gear to slow down enough or stop, so that
the shift will be less brutal.
4th Gear-5th Gear dead spot:
Someone a while ago was talking about a dead spot between
4th and 5th, that felt much like neutral If you look at the pictures, you
will see that the there is no difference between the positions of 4th gear
and 5th gear when you are in 4th gear, 5th gear or neutral. It is the
movement of the 2nd/3rd pinion that differentiates these gear positions.
When you shift from 4th to 5th, you are actually passing through
neutral.
Why the shifts for other gears are so smooth:
The
reason that the shifts from all the other gears are so smooth is
because whenever the bike is moving (thus, the countershaft is
spinning), every gear on the shaft is spinning as well. This allows
the dogs to engage with a softer impact, making the shift smoother.
How a broken or bent shift fork could ruin your day:
If
a shift fork were to break or bend severely, this could cause two
gear ratios to be engaged at the same time. These forces would work
against each other immediately, causing the gear box to lock up or
grenade. In either case, you're flying through the air before you
have a chance to realize what happened. It's for this reason that
being easy on the shifter is so important. It is the force of your
foot combined with some springs that cause the shift cam drum to
rotate and move the forks.
About these photos: I bought this XS11 for $300 with the
knowledge that I would have to rebuild this transmission. This is a
task that I have never done before. This is the second time I have
rebuilt this transmission in the month that I have had the
motorcycle. The first time I tried the "black and decker fix",
however it only fixed 2nd gear, 1st gear actually got worse. 2nd was
also hard to shift at this point. So, I bought brand new 1st, 2nd,
4th and 5th gears as well as the #3 shift fork. 3rd gear was okay.
This time the process went much quicker then the first time, you can
see from the color of the new parts that they haven't seen much oil,
heat or pressure yet.
Authored by Steve Borenstein.
Please feel free to email me with any questions or comments. If any
information here is incorrect, please inform me and the website
owner.
|
