I follow a couple forums about Honda Rebel motorcycles. There is a great deal of
information available there about repair and maintenance, and users share their
experiences about various modifications they have made to their bikes. One such
mod that has been discussed at length is replacing the fourteen tooth drive sprocket
with a fifteen tooth. There seem to be strong feelings on the subject either way, and
since the process is relatively inexpensive and completely reversible, I decided to try
it myself. Below are some photos I took during the surgery for the benefit of those
who may be entertaining the idea of giving it a try. Since it involves removing the
chain guard and loosening the rear wheel, I cleaned the chain at the same time.
Mine is an ‘09 CMX 250 built for the U.S. market. Details on other Rebels may vary.
I decided that it would be easiest to accomplish this with the rear wheel off the floor.
There are lifts available that are perfect for the job. They hook onto the sides of the
swing arm, and allow you to lift the back end quite easily. I don’t have one, so I used
a floor jack, with some
blocks of 2x4 and plywood
to support the weight of
the bike from the front of
the swing arm. It is not a
good idea to jack your
bike up by any part of the
exhaust system. 
I find it preferable to
loosen the axle before
jacking the wheel up,
because it’s more stable
when torquing on the axle.
Use a shallow socket on
the end of the axle, and
another on the axle nut to
loosen it. Once the axle is
loose, jack the rear end
up. If you have one of
those nifty lift things, good
for you. If you use a jack,
lift the bike up by the front
of the swingarm, using the
blocks of wood to keep
the exhaust off the jack.
check carefully to make
sure you don’t catch the
chain, smash any hoses
or wires, etc. The rear of
the bike should be just
high enough to get the tire off the
ground, and stable enough not to fall
if you push on it some. I use a block
of 2x4 under the side stand to
stabilize it. There is a threaded stud
sticking out of the end of the swing
arm on either side. It has an
adjustment nut, and another nut to
lock the adjustment nut in place.
Loosen the outer nut on each first.
Use caution not to use too much
force on these nuts, as the
adjustment stud will break easily if
you over torque, or forget to loosen
the locking nut before wrenching on
the adjustment nut. Loosen the
adjusters on both sides to allow the
wheel to slide all the way forward.
Next,  remove the chain guard. There
are three screws. Two are in plain
sight; the third is hidden behind the
chain. After that, remove the gear
shift lever. The shift lever clamps onto
the end of the shaft by means of a
bolt. The head of the bolt is to the
rear of the top end. Remove the bolt, and pull the shift lever off by pulling straight out
with your fingers. It shouldn’t take much force. Behind that is the rear crankcase
cover. It’s held in place by two screws. The lower screw also holds a clip that keeps
some wires in place. Remove the two screws and the clip. The cover should slide
straight out toward you. Behind it you will see the front sprocket, and probably a
deposit of crud that has been thrown
off the chain. Depending on whether
you use oil or wax on your chain, the
crud will either be oily or waxy. On the
face of the sprocket, you will see an
oval  retainer, held in place by two
small bolts. I found it easiest to
remove them with the transmission in
gear, but there are several ways to
immobilize the sprocket. The torques
involved are not major. With the bolts
out, the oval retainer should rotate on
the shaft so that it will line up with the
splines and slide off. There should be
enough slack in the chain to allow
you to pull the sprocket out with the
chain around it. It should slide out
with some wiggling. This is the point
at which I cleaned both the chain,
and the area around the shaft. I used
kerosene and a Grunge Brush. If you
don’t have a Grunge Brush, get one.
They are available online, and at
some retailers. Drop the chain off the
rear sprocket, and let it hang down
into a container of kerosene. You
should have enough slack to soak
and scrub about a foot of chain at a
time. While a section is soaking,
scrub the area around the shaft, as
well as the inside of the cover with
the brush and a rag damp with
kerosene. I was careful not to let
kerosene come in contact with the
bearings around the shaft. I don’t
know for a fact that it will hurt
anything, but thinning the oil there
probably is not good.
 The next step is to put the new
sprocket in place. I doesn’t look like it
will fit with the chain around it, but it
will. I put it on without the chain first,
just to get a feel for how it will line up
and slide in place. Put the chain
around the new sprocket, line it up on
the shaft, and rotate it slightly to get it
lined up with the splines. It will
probably take some wiggling to get it
to go on, but it will.
Please note that the side of the sprocket with markings on it faces in. The side facing
out has no stampings. The rest is pretty straightforward reassembly. Put everything
back in place, torque to specs, adjust the chain tension, lube the chain, and align the
rear wheel.
I haven’t put many miles on my bike since the transplant, so I can’t say anything
definitive about the results. The ratios have changed so that each gear has a slightly
higher range. This doesn’t appreciably increase top end speed, but it does mean that
my RPMs are lower at a given speed, and so far I’m happy with it. I’ll update in a few
hundred miles when I know more.