Sherco Ignition Timing Guide

Sherco Ignition Timing Guide
This guide is designed to provide the Sherco owner with
instructions on how to check and adjust the ignition timing on
the 1999 – 2003 series Sherco 1.25, 2.0, 2.5 and 2.9 models.
The bike photographed in this manual is a new 2003 2.9, but the
same principles apply for the 1.25 through 2.5 models, too. The
same brand and type of magneto/ignition is used from “99 – 03”.
There may be some minor appearance changes.
You will require a flywheel puller, which is available from Ryan
Young Products.
You may want to obtain a Sherco timing pin and a dial indicator.
The Sherco timing pin is available from Ryan Young Products,
the dial indicator will have to be obtained from a tool supply
house. For a location see page 16.
If you have any questions about the procedure, please call Ryan
Young Products at 1-800-607-8742.
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Ignition Timing Comments
For general purpose use, we recommend maintaining the factory ignition timing setting
and adjusting one’s riding style to the performance of the bike. In the event that the
factory setting does not meet your performance requirements due to altitude or riding
style, this manual will define the steps required to modify the factory timing.
Note that the timing setting of the particular bike photographed in this manual was
slightly more advanced than the specification. The owner of the bike is very satisfied with
the performance and it is not pinging, for this bike it was unnecessary to change the
timing to the precise factory setting. The factory timing setting is a compromise between
achieving maximum RPM and smooth low end response plus ease of starting. The stator
plate tends to be factory positioned in such a way that it is biased more in the advanced
direction. Therefore, while there is some adjustment room to advance the timing, there is
much more room to retard it.
Why Advance the Timing Beyond the Factory Setting?
Generally speaking, there may be little overall advantage. The result will create quicker
bottom end engine response and an increase in idle speed, but the motor may also kick
back more when starting, or show some tendency to ping when hot under quick
applications of throttle. Advancing beyond factory settings is beneficial for riding at high
altitudes, as it will return some of the engine response lost from thin air. To experiment,
adjust the timing to the full advanced position, as far as the slots allow.
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Ignition Timing Comments, continued
Why Retard the Timing Beyond the Factory Setting?
Retarding creates a softer low-end engine response for riders who rarely ride at maximum
RPM. Other benefits include: easier starting and much smoother slow riding in first gear
with no clutch, and preventing wheel spin in slippery terrain. Retarding will necessitate an
increase in idle speed which can be achieved by turning in the carb idle screw.
To experiment with retarding, first fully retard the ignition as far as the slots will
allow. Note that adjusting the timing in small, precise increments will not provide an
appreciable performance difference. Increase the carburetor idle speed appropriately,
then test ride the bike. Next, try a setting half way between factory and fully retarded. By
testing the bike’s performance at extreme timing settings, it becomes easier to chose a
setting suitable for riding style or conditions.
Idle Considerations
The idle, regardless of timing setting, should be adjusted to prevent engine stalling. The idle
speed is correctly adjusted when the bike can creep forward (with no throttle) in first gear by
merely dragging the clutch. Perform this test on flat, smooth ground.
Note: Use caution when moving the stator plate as damage to the wiring harness can occur.
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Factory Ignition Timing Specifications
1.25
2.0
2.5
2.9
1999
-------- -------- 2.5mm --------
2000
3.0mm 3.1mm 2.5mm 2.7mm
2001
2002
3.0mm 3.1mm 2.5mm 2.7mm
3.0mm 3.1mm 3.8mm 3.8mm
2003
3.0mm 3.0mm 3.0mm 3.0mm
These specifications are Before Top Dead Center (BTDC)
Sherco Ignition Timing, Rev.0902
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Remove gear shift lever bolt
Remove ignition cover
5 mm Allen
wrench
Remove the gear shift lever bolt by using a
5mm Allen wrench. Insert the wrench through the
hole in the skid plate. Holding the gear shifter up
in second gear makes it easier to align the wrench
into the head of the bolt.
Pull the gear shift lever as far as possible
towards the chain. (The chain does not have to be
removed in order to remove the ignition cover and
flywheel)
Remove the three ignition cover bolts by
using a 4mm Allen wrench.
Carefully remove the ignition cover-which
requires a little twisting and some outward
pressure on the gear shift lever. The shift lever
may also have to be pressed down into the first
gear position.
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Glue gasket to cover
Remove flywheel
Chisel marks
Factory paint mark
Inspect the rubber ring gasket for cracks
or cuts while the ignition cover is off.
Replace if necessary. We recommended
applying a ring of high grade silicone sealant
to further improve the seal of the rubber ring
gasket.
Tap a chisel-mark across the flywheel
retaining nut and the crankshaft by using a small,
sharp chisel. This mark serves as a reference
point for retightening the flywheel in its original
position during reassembly.
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Remove flywheel, cont.
View showing the flywheel
retaining nut removed.
Remove the flywheel retaining nut using a small
impact tool fitted with a 19mm (3/4”) socket. Note
that there is no washer under the nut.
Sherco Ignition Timing, Rev.0902
Back off the push bolt and thread
the Sherco flywheel puller into the
flywheel, until the threads bottom.
The puller does not have to be
tightened with a wrench.
7
Remove flywheel, cont.
3 Bolts
Hold the flywheel removal tool with either
an adjustable wrench as shown, or a 24mm
(15/16”) open end wrench. Tighten the removal
tool screw by using a small impact tool fitted
with a 16mm (5/8”) socket until the flywheel
comes loose from the crankshaft.
Carefully remove the flywheel - it requires
a little twisting and some outward pressure on
the gear shift lever. Be careful not to misplace
the alignment key.
3 Slots
View showing the flywheel removed with the
stator assembly exposed. Notice that it is retained
with three bolts, and that the backing plate is slotted.
Note: Spraying the inside of the case, the stator
plate, and the flywheel with clear lacquer will help
prevent corrosion.
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Mark factory timing setting
Tap a straight,
sharp chisel mark
across the stator plate
and its fixing bracket to
identify the factory
position of the stator.
Chisel mark
With this mark, the
timing can always be
returned to the factory
setting, no matter how
many timing changes
are made.
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Check the timing using a dial
indictor and timing pin
TDC chisel mark
Factory mark
on flywheel
Remove the spark plug
by using a 13/16” spark
plug wrench.
Install the dial
indicator into the
cylinder head.
Follow the
instructions included
with the dial indicator to
set it at “0” for top dead
center.
Reinstall the flywheel on the
crankshaft, but do not yet install the
flywheel retaining nut.
For future reference, use a small,
sharp chisel and mark the Top Dead
Center location on the engine case, as
shown above.
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Check timing, cont.
Hand-rotate the
flywheel clockwise,
watching the dial
indicator needle.
When it is close to
the factory
specified timing,
insert the timing
pin. The pin should
fit into the timing
hole in the stator
plate. Do not insert
the pin too far,
which will make it
difficult to remove.
Read the dial
indicator with the
pin inserted. This
reading represents
the factory timing.
Note: Engine
rotation is
Counterclockwise.
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Change timing
Check timing, cont.
Remove the timing pin and the flywheel.
To advance the timing, loosen the three bolts of the
stator plate (4mm Allen wrench), and rotate the backing
plate Clockwise.
The factory timing on this engine
reads 3.51mm BTDC. The factory
specification is 3.0mm BTDC, which
means that this particular engine’s timing
is advanced. The dial actually reads 3.49
but since the indicator is moving away
from zero you have to read it as 3.51.
To retard the timing, loosen the three bolts of the stator
plate, and rotate the backing plate Counterclockwise.
Once the backing plate has been moved into the
desired position, reinstall the flywheel. Check the reading
on the dial indicator, repeat the process until the correct
desired dial indication is achieved.
Note: Use caution when moving the stator plate as damage to the wiring harness can occur.
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Reassembly
Generally, reassembly is the same as assembly, but performed in reverse
order.
Remove the dial
indicator and reinstall the
sparkplug. Hand-tighten
the sparkplug, and then
tighten it ¾’s of a turn
using a 13/16” spark plug
wrench.
Install the flywheel, aligning
the keyway in the flywheel with
the key in the crankshaft.
Apply a liberal coat of “blue”
loctite to the flywheel retaining
nut and install it using a small
impact tool fitted with a 19mm
(3/4”) socket.
Sherco Ignition Timing, Rev.0902
Tighten the flywheel retaining nut
so that it is approx. 5 degrees (about
2mm) beyond the original factory
paint marks/chisel marks.
The factory torque is 73.2 ft lbs.
13
Reassembly, cont.
Reinstall the ignition cover. Apply anti-seize
to the three retaining bolts. Do not over- tighten
these three bolts. Use a 4mm Allen wrench.
Reinstall the gear shift lever bolt by using
a 5mm Allen wrench.
Reinstall the fuel tank, reconnecting both
the fuel line and the overflow line.
Reinstall the rear fender.
Test ride the bike to confirm that the
settings are suitable.
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Changing ignition timing without using a
dial indicator
1. Follow Steps 1 through 10.
2. Refer to Step 16 (page 12): To advance the timing, loosen the three bolts (4mm Allen wrench) and rotate
the backing plate Clockwise.
3. To retard the timing, loosen the three bolts and rotate the backing plate Counterclockwise.
4. Make the desired adjustments, then reinstall the flywheel and the flywheel retaining nut. It is not
necessary to torque the nut at this time because you may want to remove it. The nut should be tightened
enough to ensure that the flywheel does not come off during the test ride.
5. Test-ride the bike to determine if the performance results are satisfactory, and if so, follow steps 18 – 21
to complete this project. If the performance is not satisfactory, repeat steps 2 – 4 above.
Note: Use caution when moving the stator plate as damage to the wiring harness can occur.
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Motorcycle Timing Gage
Manufacturer: Central Tools, Inc
Manufacturer #: 6491
ToolSource #: 91545
This item is available from “ToolSource” 1-888-220-8350
http://toolsource.com:888/ost/Default.asp
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