Getting it Straight -- Snowmobile Alignment
Part II
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, you can check certain alignments. In our last
installment we covered: Drive sprockets to each other; and
Drive axle and suspension to tunnel and track.
This type of work is time consuming, so it's normally a spring
or early fall job. Plan on
at least 20 hours to complete this type of project, much more
if this is your first time taking some of these areas apart. 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.
Drive axle to jackshaft
Begin by loosening the bolts and the bearing locking collar [shown in photo
below with a blue line] of the clutch-side jackshaft bearing. Even
in brand new bearings you'll notice that there is some play or
movement. You can feel this by wiggling the shaft up and down, and
left to right. Find the center of the circle that is created by
experimenting with the full range of motion. Using your carpenter's
square, measure to make sure the jackshaft is square with the frame.
If the jackshaft is not square with the frame, you will need to shim
the chaincase in the appropriate corner to move the jackshaft into
a square position. The mount on the clutch side may require the
mounting holes to be slotted if you can't move the jackshaft far
enough. A file or die grinder will be sufficient for this task.
When the adjustments have all been made, and the jackshaft is
square, make sure to scribe a mark around the mounting brackets so that
if the jackshaft is ever removed, you can line everything up to the correct
markings that you have just squared.
Note that if you are working on a restoration, you should check that
the jackshaft is not cracked or damaged in any way before proceeding.
Also, check the bearings while everything is apart. This is done
by confirming the amount of play and if it spins freely, or feels
rough when turned.
In the picture below, the jackshaft, chaincase, and drive axle have
been removed from the sled. The red lines point to the chain case
mounting points, while the blue line points to the jack-shaft
bearing and locking collar.
Next, you check the axial play -- side to side, or left to right
movement -- of the drive axle. This may have to be spaced to use
manufacturer's specifications. Shims can be placed between the left
housing or the right housing, to keep the axle centered in the
track tunnel.
Gear Alignment
You need to make sure your gears are properly aligned to avoid
having your chain run crooked. This can cause lost performance and
excessive wear on your moving parts.
To align the gears, you place a straight edge across all four
edges of the gears as shown in the picture below. The straight edge
should touch all the way along both gears, if they are straight.
If not, you will have to add or remove shims from behind one or
the other gear, making sure that the chain will not touch
either the chain case or cover. The chain must run freely between
the chain case and the cover.
Drive clutch to driven clutch
Clutch alignment is accomplished by shimming the secondary clutch
and moving the engine. You require the manufacturer's specification
sheet BEFORE you begin making any adjustments.
Begin by opening the secondary clutch and inserting a bar. The clutch
will close over the bar, holding it firmly in place. This will allow
you to use the bar to measure the specifications for
the front and back of the primary
clutch as shown below.
If the measurements are not within the range required in the
specifications sheet, you need to loosen engine mounts and twist
or move the engine ahead or backwards until they are reached. You
may add or remove shims from the secondary clutch, to move it left
or right only. Make sure that the secondary clutch doesn't contact
the frame when it is completely opened.
Your specifications will also provide you with a correct
center-to-center measurement for your clutches, which will be
set with the above adjustments. Make sure to recheck this before doing
the belt deflection.
Next, you will move to belt deflection. You check this in either of
two methods, both illustrated below.
1. Set your square bar on top of the belt, and with a belt
deflection tool, which is available at most automotive stores,
push down halfway between the clutches. Exerting the pressure
indicated in the spec sheet for your sled, the belt should push down
the distance listed in the spec sheet.
2. Instead of using a belt deflection tool, you may use
a fish scale or spring scale and a ruler. Again, you are looking
for the specifications listed for your sled.
If the belt deflection is incorrect you will have to open or
close the secondary clutch with the screws [indicated with
the red line in the picture under #1 above] on some models. On others, you
will have to take apart the secondary clutch and add or remove shims.
Add shims to loosen the belt, remove shims to tighten the belt.
In the photo below, you can see that a snowmobile belt has
a directional arrow on it. The belt must be installed so that
it spins the correct way, or points forward on the top [points
towards the sled's front bumper].
Even belts that do not have an arrow on them should always be
installed the same way after they have been used. In order to remember
which way it has been installed, I always install a belt so that
I can read the writing when standing beside the sled. If installed
the opposite way, the writing will be upside down.
Your sled is now aligned and completely reassembled. There are various
different videos available from performance shops that you
can purchase to watch this done step by step at home. If you are
a novice mechanic, I highly recommend you purchase one. Besides,
everybody needs a good collection of snowmobile performance videos!
This article originally appeared in SnowRider Online Magazine in January 2002.
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