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FORM 97140090
INSTALLATION INSTRUCTIONS
Ignition Model #35496
CAUTION: CAREFULLY READ INSTRUCTIONS BEFORE PROCEEDING. NOT LEGAL FOR USE OR SALE ON POLLUTION CONTROLLED VECHICLES
OVERVIEW
ACCEL Ignition Model 35496 is intended for use with Harley-Davidson®
Evolution® type motorcycle engines. The Model 35496 replaces the original equipment (OE) electronic ignition system on 1978-99 models. The unit
mounts in the gear case cover and uses the standard H-D® timing rotor.
It can also be used on earlier models with breaker points and mechanical
advance.
The Model 35496 offers adjustable advance, adjustable RPM limit settings in 100 RPM increments, and switch selectable single or dual fire
modes. Single fire mode improves starting, reduces the occurrence of
backfiring at low RPM, and improves power at high RPM. A red status LED
flashes when the engine reaches top dead center (TDC) and allows easy
static timing. The status LED also provides diagnostic information. A green
VOES LED illuminates when the VOES (vacuum switch) input is active.
AVOIDING HEAT RELATED FAILURES
Heat kills electronics. The Model 35496 uses electronic devices rated
for operation at 105 deg C (221 deg F), the highest rating available. The unit
can tolerate somewhat higher temperatures, but exposure to temperatures above 125 deg C (257 deg F) will greatly reduce life expectancy. We
sometimes see problematic applications where several module failures
have occurred. The failure mode is a classic thermal intermittent where the
module stops firing one cylinder when it gets hot. We have found that these
problematic applications share one or more of the following characteristics:
INSTALLATION
1. Turn off the ignition switch and disconnect the battery
ground cable before proceeding.
• VOES switch removed or non-functional. All street driven engines
require vacuum advance. Without vacuum advance at idle and part
throttle, thermodynamic efficiency is reduced and engine temperatures
increase significantly.
• Improper carburetor jetting resulting in lean air/fuel ratio (AFR). A lean
AFR will cause the engine to run very hot. All performance engine
modifications necessitate carburetor rejetting. Carburetors are never
correctly jetted out-of-the-box. The only practical means of correctly jetting a carburetor is to test the motorcycle on a chassis dyno
equipped with an exhaust gas sniffer.
• Lack of an oil cooler on a 95 CID or larger engine.
• Exhaust pipe without heat shield in close proximity to the nose cone. If
any of the above applies to your application, the Model 35496 may be
exposed to excessive temperatures resulting in reduced life expectancy. Use an infrared thermometer to check the module temperature.
INCLUDED AND ADDITIONAL REQUIRED PARTS
All units include a parts bag with crimp terminals for coil and VOES
hookup.
FL series Big-Twin® models manufactured prior to 1985, FX series BigTwin® and XL Series Sportster® models manufactured prior to 1984, all
Sportster® 1200S models, and all models with original equipment breaker
points will require H-D® timing rotor P/N 32402-83 or an equivalent aftermarket part.
2. Refer to Figure 1. Remove gear case cover plate and mounting hardware. You may have to drill out two rivets that hold
the cover (reassemble with supplied self-threading screws).
Remove the sensor plate or breaker points. Make sure that
the correct H-D® P/N 32402-83 timing rotor is installed.
3. You can completely remove the OE ignition harness and
external module (1980 and later models) if desired. However,
you must disconnect all OE wires from the coil except the
white/black wire from the engine stop/run switch.
4. Install the Model 35496 unit. Wrap one turn of electrical tape
around the end of the protective wire harness sleeve. This will
compress the sleeve and allow you to easily feed it through
the cable exit hole in the gear case cover. The tape will also
keep the sleeve end from fraying. You will have to enlarge the
hole with a drill on early models and some Sportsters®.
5. Rotate the unit and then place it into position as shown in
Figure 2. Be careful to avoid damage to the black plastic Hall
Effect sensors on the bottom of the unit.
6. Route the wiring harness along the side of the unit and install the
mounting standoffs as shown in Figure 3A for Big Twin or 3B for
Sportster® models. Do not fully tighten the standoffs or install
the outer cover plate until after the static timing procedure.
Figure 1 - Feeding Harness Through Exit Hole
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Figure 2 - Installing Unit (Note Orientation)
7. Route the wire harness along the frame tubing to the ignition coil.
Make sure that the harness is clear of hot exhaust areas and cannot
chafe against sharp edges. Secure the harness with nylon cable ties.
8. Refer to the appropriate wiring diagram. Use the dual fire hookup
shown in Figure 4 if you have an OE coil or other coil with two primary
terminals. Use the single fire hookup in Figure 5 if you are installing
an aftermarket coil with three primary terminals. Use appropriate
crimp terminals for coil and VOES hookup. With the exception of the
tachometer and rear coil section (single fire only), standard H-D®
wire color codes are used. Tape up any unused wires.
9. Install the supplied Weather Pack connector set on the brown
tachometer wire as shown. If a tachometer is not used, seal the end
of the mating plug with silicone RTV and use it as a protective cover.
Use a proper Weather Pack crimping tool or solder the terminals.
10. Single Fire Tach Hookup. If your motorcycle had a tach before installation of the ACCEL module, the tach was connected to the pink coil
wire. When you connect the tach direct to the ACCEL module as
shown in Figure 5 for a single fire application, you must make sure
that it is not still connected to the pink coil wire. Trace the wire going
all the way back to the tach to avoid an inadvertent coil connection.
NOTE: The unit is grounded by means of the gear case
housing. The mounting surface must not be anodized or
painted.
Figure 3A - Finished Big-Twin® Installation
11. Reconnect the battery ground cable. Complete the setup and timing
procedures given on pages 3-7.
12. Reinstall the cover plate using two supplied 10-24 x 1/4” socket head
screws and lock washers in place of the original rivets. You will have
to tap the rivet holes on the inner plate (do this with the plate removed
from the bike to avoid damaging the ignition). You can use the supplied 10-24 x 3/8” self threading screw as a tap.
Figure 3B - Finished Sportster® Installation
CAUTION: Engine damage from excessive timing advance may result if the purple/white VOES wire is
inadvertently shorted to ground.
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OPERATING MODES
A single 10 position rotary switch is used to select the operating mode.
Switch settings are as follows:
0 Street advance curves, dual fire, multi-spark disabled
1 Street advance curves, dual fire, multi-spark enabled
2 Street advance curves, single fire, multi-spark disabled
3 Street advance curves, single fire, multi-spark enabled
4 Race advance curves, dual fire, multi-spark disabled
5 Race advance curves, dual fire, multi-spark enabled
6 Race advance curves, single fire, multi-spark disabled
7 Race advance curves, single fire, multi-spark enabled
8 Not used
9 Race advance curves, single fire, kick start
The engine will not run if the mode switch setting does not match the
wiring hookup (i.e. you cannot select single fire mode with a dual fire coil
hookup).
Advance curve families are shown in Figures 6 and 7. Use the street
advance curves (mode switch settings 0-3) for stock or mildly modified
engines. Use the race advance curves (mode switch settings 4-7) for high
compression engines.
We recommend that you enable multi-spark. When multi-spark is
enabled, a continuous series of sparks is fired from the advanced timing
point until TDC. Most air-cooled engines require relatively cold spark plugs
to prevent detonation under high load. Multi-spark reduces the consequent
tendency for plug fouling at idle.
Switch setting 9 selects race advance curves, single fire, and kick start
mode. Multi spark is disabled.
Figure 4 - Dual Fire Wiring Diagram
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Figure 5 - Single Fire Wiring Diagram
TUNING TIP: Lean air/fuel ratio (AFR) increases the tendency for spark knock. Check AFR and rejet
carburetor before optimizing ignition timing. Test the motorcycle on a dyno with an exhaust gas sniffer.
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RECOMMENDED TIMING SETTINGS
0
5
10
15
20
25
30
35
40
0 1000 2000 3000 4000 5000 6000 7000
ENGINE RPM
ADVANCE (DEG)
MA X A DV ANCE A T W IDE OPEN THROTTLE
MIN A DV A NCE A T WIDE OPEN THROTTL E
MA X A DV ANCE WITH V OES GROUNDED
MIN A DV A NCE WITH V OES GROUNDED
Street and race advance curve families are shown in Figures 6 and
7. Each family has minimum and maximum curves. The advance slope
switch allows you to run an advance curve in between these minimum and
maximum curves. Advance slope switch setting zero corresponds to the
minimum advance curve. Switch setting 9 corresponds to the maximum
advance curve. Higher switch settings result in a more aggressive curve.
Tuning a particular engine setup always requires some trial and error
experimentation, but maximum power is usually obtained by using the highest advance setting possible without audible spark knock. Some recommended starting points are given below:
For stock engines run on normal pump gas (87-89 octane), use the street
advance curves and advance slope setting 5.
For stock or mildly modified engines run on 92 or higher octane gas, use
the street advance curves and advance slope setting 7.
For high compression engines, use the race advance curves and
advance slope setting 2.
You can adjust the initial timing by rotating the ACCEL module relative to
the gear housing (clockwise rotation increases initial timing).
If you experience spark knock only at low RPM, you can try reducing the
initial timing while maintaining an aggressive advance slope for maximum
power at high RPM by increasing the advance slope switch setting. If spark
knock is a problem at high RPM, decrease the advance slope switch setting.
Note that the wide-open throttle (WOT) curves are active unless the
VOES input is grounded. During idle and cruise, the VOES input is grounded
(green VOES LED illuminated) and the low manifold pressure (MAP) curves
are active.
RPM LIMITER SETTING
You can set the RPM limit from 3,000 to 9,900 RPM in 100 RPM increments by means of two rotary switches. The RPM limit is X100 switch setting (i.e. 57 = 5,700 RPM). Inadvertent settings below 3,000 RPM are ignored
and result in a 3,000 RPM limit.
The Model 35496 uses a newly developed RPM limiting algorithm that
has been highly optimized for odd firing V twin engines. When the engine is
held against the RPM limit, cylinder firing is always paired. This eliminates
a torque couple and results in very smooth operation compared to random
or sequence type RPM limiters.
Set a safe RPM limit that is appropriate for your engine. Most Evolution®
engines with OE valvetrain components should not be run over 5,700 RPM.
STATIC TIMING PROCEDURE
1. Timing marks are located on the flywheel and may be viewed by
unscrewing the inspection hole plug. Most engines will have both TDC
and advance timing marks for the front cylinder as shown in Figure 8. If
you are not sure, refer to your shop manual. You can also identify the
TDC mark by removing the spark plugs and rotating the crankshaft (turn
rear wheel in high gear) until the front piston comes up on TDC.
2. For static timing, you must rotate the crankshaft so that the front piston
is at TDC on the compression stroke. Remove spark plugs and rotate
crankshaft. If you place your thumb over the spark plug hole, you
will feel pressure as the piston comes up on the compression stroke.
Continue rotating the crankshaft until the TDC mark is precisely centered
in the inspection hole.
3. Ground the spark plug cables to avoid a shock hazard. You can use small
jumper wires with alligator clips for this purpose.
4. Turn on the ignition switch. The red LED is used as a timing indicator.
Note that the LED does not immediately illuminate when power is first
turned on. Rotate the ignition unit back and forth until the red LED illuminates. Then slowly rotate the unit clockwise until the LED goes out. Note
that the LED goes out at TDC.
5. Tighten the standoffs to secure the unit. Turn off the ignition switch and
reinstall the spark plugs.
PRECISE TIMING PROCEDURE
1. Use a standard timing light. Note that most dial-back type timing lights
will not work correctly with dual fire applications. If you have a dial-back
timing light, set the dial-back to zero. Do not enable multi-spark while
setting timing.
2. The precise timing procedure is based on using the 35° BTDC timing
mark and race maximum advance curve with VOES grounded that
reaches 35° BTDC around 2,000 RPM (refer to Figure 7). To use this procedure, you must have a VOES switch connected. If a VOES switch is not
used, you must ground the purple/white wire while setting the timing.
3. Set mode switch to 4 for dual fire or 6 for single fire. Set advance slope
switch to 9. Connect the timing light pickup to the front cylinder spark
plug cable. Loosen standoffs securing the ignition unit. Run the engine
at a steady speed just over 2,000 RPM. Rotate the ignition to center the
35° BTDC timing mark in the inspection hole. Tighten standoffs and verify
that the timing has not changed. When done, change mode and advance
slope switches back to desired values.
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Figure 6 - Street Advance Curves
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Figure 7 - Race Advance Curves
0
5
10
15
20
25
30
35
40
0 1000 2000 3000 4000 5000 6000 7000
ENGINE RPM
ADVANCE (DEG)
MA X A DV ANCE A T WIDE OPEN THROTTLE
MIN A DV A NCE A T WIDE OPEN THROTTL E
MA X A DV ANCE WITH V OES GRO UNDED
MIN A DV A NCE WITH V OES GROUNDED
Figure 8 - Front Cylinder Timing Marks
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GENERAL RECOMMENDATIONS
Coil primary resistance must not be less than 3 ohms. Most OE style dual
fire and aftermarket single fire coils meet this requirement. Coils for the new
Twin Cam engine have low primary resistance and are not compatible.
Due to the short lengths involved on motorcycle applications, energy losses
in spark plug wires are insignificant. OE carbon core suppression cables
will deteriorate after several years. For a more durable replacement, we
suggest spiral core spark plug cables.
The ACCEL module is compatible with all modern “ground sensing”
type tachometers including H-D® OE and Autometer units. The red status
LED is internally connected to the tachometer output. If the red status LED
blinks, the tachometer output should be functional. Some early tachometers
require a high voltage trigger pulse. In this case, you will require a commercially available tachometer adapter.
VOES CONSIDERATIONS
The vacuum switch (VOES) provides the vacuum advance required by
all street driven engines. Additional advance under low manifold pressure
conditions improves idle stability and fuel economy. Most 1980 and later
motorcycles are equipped with a OE VOES. Without vacuum advance at idle
and part throttle, thermodynamic efficiency is reduced and engine temperatures increase significantly.
The VOES is normally open. At low manifold pressure (or manifold
vacuum greater than about 5 inch-Hg), the VOES grounds the purple/white
wire and causes the ACCEL module to generate additional timing advance.
The green VOES LED illuminates whenever the VOES input is active (timing
advanced).
The use of a VOES is required for proper operation of the ACCEL module.
If your motorcycle did not include an OE VOES, you can use H-D® VOES P/N
26566-91 for stock or mildly modified engines.
TROUBLESHOOTING FLOWCHART
Follow the troubleshooting flowchart shown on the next page. Experience
has shown that most units returned for warranty are OK and another problem, such as a defective coil, is later identified.
TROUBLESHOOTING TIP: If you are installing an internal (nose cone) ignition for the first time and the
engine will not start, the most likely problem is improper static timing. Make sure that the front piston
is at TDC on the compression stroke and not on the exhaust stroke.
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ACCEL IS A TRADEMARK OF ACCEL PERFORMANCE GROUP
10601 MEMPHIS AVE. #12, CLEVELAND, OHIO 44144
216.688.8300 FAX 216.688.8306
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