Getting it Straight -- Snowmobile Alignment
Part I
Alignment of every moving part is critical to how easy the sled will roll, so
performance gains can be made by making sure all parts of the sled are
properly aligned. Whether you've got a brand new sled that you're
looking for top performance out of, a relic you're restoring, or
something in between, these are a few alignments you can examine:
- Drive sprockets to each other
- Drive axle and suspension to tunnel
- Drivewheels to track
- Drive axle to jackshaft
- Drive clutch to driven clutch
This type of work is time consuming. It takes me two full days, or
at least 20 hours to complete this type of project. No special tools
are required, other than those used in regular sled maintenance, so
if you have the time and basic skills, you can likely accomplish
the job on your own.
In addition to basic tools, you'll need a carpenter's square to
align various parts. The complete sled will be torn down, except for
engine, which is only removed from the frame. While this isn't
absolutley necessary, it makes life a lot easier!
The hood, seat and gas tank may also be removed, for complete
ease of working on the chassis. In the long run, this will likely save you time.
Drive Sprockets
Drive sprocket spacing should correspond with the space between the
drive lugs on internal drive tracks. While the sample shown has
three separate wheels, yours may only have two, or as many as four.
Each wheel has paddlesides, on one or both sides, that fit into
the drive lugs in the track. The center of the drive wheel should
sit exactly in the center of the space between the track lugs.
On external drive tracks the sprockets should run to the outside of
the holes in the track. This type of track works by having the drive
wheels actually drive in the holes to turn the track.
The manufacturer provides specs for your particular drive wheel
spacings. You will have to ask your local dealer for this information,
or purchase a shop manual for your model of sled. Check each
measurement as shown in the manual. Remember that your
sled is assembled on a production line, so you may occasionally find
one that it is 1/16 of an inch or so out. For maximum performance this
can be corrected.
The drive sprockets must also be aligned to one another. This is done
by using the indexing marks that appear on one of the top edges.
The marking is usually a dot or an arrow. This is done to keep the
drive lugs or teeth [necessary on internal and external drive tracks]
in time with each other. Most drive axles are hexagonal or have
six sides, so
unless you had either six or twelve teeth they wouldn't line
up with each if one sprocket was out 1/6 of a turn.
It's rare that you would find a new production sled has a problem in
this area. However, if the indexing marks don't line up, you'll need
to press off the sprockets and press them on correctly. This will
require more than basic mechanical equipment.
If you are working with a used sled, or one you are restoring from
scratch, you may find that an error has been made with a previous
installation, or they are worn out and need to be replaced. Press off
the worn drive sprocket and replace with new or used parts.
Also, you should check to make sure the axle is not bent or
that the splines for the chain sprocket are not twisted or worn as
shown in the picture above. A
visual inspection should be sufficient. If you lay the
drive axle on a flat surface, rotating to all six sides, it should
consistently lay flat. To check for a bent end on the chain
sprocket side, measure the distance of the tip to the flat
surface on all six sides -- it should be the same with each
rotation.
Drive Axle and Suspension to Tunnel
The first thing to align is the drive axle to the tunnel.
Use the carpenter's square and position it with the short side
touching all of the wheels on the
drive axle and the long side down the inside of the tunnel.
It should be exactly square. [see photo below]
Manufacturer's tolerances may allow some leeway, so if you want
it exact in your new sled you may have to make some changes.
If it's not square, you will have to slot the mounting holes [see
illustration below]
in the frame
with a file or a die grinder, on the
bearing cap side until it is. You will need to move the drive axle forward
or backward until it is completely square with the frame.
Once the drive axle is square, mount the rear suspension. To
check rear suspension alignment you begin by determining if the
sliderails are running at 90 degrees to the drive axle. Measure
the distance from the outer edge of the sliderail to the inner
edge of the tunnel at both ends of each each side.
It should be the same in all measurments. If
they are running to one side or the other, you cut off a portion of
the suspension mount and shim the opposite side.
In the image above, you can see the drive
axle and suspension mounted into the tunnel of the sled.
If you're working on an older model, you'll also check for wear
at any moving part. A rear suspension that is bent will not be
able to be aligned, and must be replaced. Once bent, a rear
suspension is weakened, so shouldn't be straightened and reused without
reinforcement.
Many older models of snowmobiles didn't have grease nipples on
major moving parts, so this is an ideal opportunity for you to add
some. Without lubrication the old suspensions seized and were
frequently damaged.
Read |Part 1I|
This article originally appeared in SnowRider Online Magazine in January 2002.
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