CDI theory:
The CDI ignition takes a
pulsed current generated by the low or high speed charge coil (depending on
engine RPM) and charges a capacitor. This stored charge is then discharged into
the primary winding of the ignition coil causing the plugs to spark (both at
once). The timing of this discharge to the coil is triggered by the arrival of a
small electrical pulse generated by the pickup coil and electronically delayed
to occur at the proper time by circuits internal to the CDI module. The
ignition, engine run and sidestand control unit provide a circuit to ground to
"kill" the ignition. There is an old saying "garbage in equals garbage out" If
any of these signals are missing or a short circuit to ground occurs in the
"kill" circuit, the CDI will be unable to function properly.
Engine
mechanical:
Suspected ignition problems are sometimes not that at all but
other engine mechanical failures so before we test electricals lets first check
the following items
1. Engine has good compression and the difference between
cylinders is small upper 90's for PSI is good for a cold engine.(5 kicks with
throttle wide open)
2. Carbs are mechanically balanced. I do this adjustment
on the bike using 1/16" music wire as a feeler guage. I adjust the idle stop
screw on the left carb untill slight resistance is felt when I slide the wire in
and out of the carb mouth under the slide. I then adjust the right carb to match
the resistance felt on the left using the balance screw. Then I reset the idle
stop screw.
3. Check auto lube pump adjustment
4. Install a set of NEW plugs. The
secondary winding of the ignition coil is attached to both plugs. In order to
complete the circuit the current must flow down one plug wire to the plug, jump
the gap, go thru the engine head to the other plug jump that gap then go back up
the wire to the coil. If you interrupt this circuit, neither plug will fire.
Engine electrical:
The RZ electrical connectors can corrode
pretty bad the engine vibration helps to maintain good contact but a bike that
has set for a while can develope electrical "ghosts" quite easilly. so lets
start by seperating, inspecting and re connecting all the electrical connections
associated with the ignition system. When that is completed take the following
readings. The following readings can be taken using the standard test leads that
come with most digital volt ohm meters. The RZ electrical system is connected
together with molded nylon "molex" or "spaid" connectors. All the initial
readings are taken with the circuit under their normal electrical load. This
means that all the connectors are connected and you take the reading by sliding
the test probe tip into the molded connector alongside the proper colored wire
untill it makes contact with the metal portion of the electrical connector.
1. On the CDI bundle find
the connector with the black wire with a white stripe running along it. put the
red test lead in along side this wire. hold the black lead against the bare
metal of a head bolt. set the meter to read resistance. With the kickstand up,
engine in neutral, the kill switch set to run and the ignition key to on you
should see greater than 30K OHMS of resistance. if you turn off the key or kill
switch the resistance should decrease to near 0.
ALL OF THE FOLLOWING READINGS ARE TAKEN DURING 5 RAPID KICKS! The object is
to keep the engine rotating long enough for the digital meter to sample the
signal and display a reading. This is easiest with the spark plugs removed, The
plug wires connected to the plugs and the metal plug bodys connected to each
other(I use tape to hold 2 plugs together) to complete the circuit.
2. On
the end of the CDI wiring harness you will find a 3 wire connector that has a
brown, red and green wire. slide your black probe in beside the brown wire and
the red probe in beside the green wire. this is your low speed winding. set the
meter to read AC volts, turn on the ignition and kick the machine over 5 times
quickly. you should see, while kicking, a reading of 25 Volts AC.
3. Now move
the red test lead to the red wire (measuring brown to red) this is the high
speed winding kick over the machine with the ignition on and you should see 4.5
Volts AC.
4. On the CDI bundle there is a 2 wire connector with a white with
red stripe wire and a white with green stripe wire. This is your pickup coil
connector. Slide your test leads in beside these 2 wires. When you kick the
starter rapidly you should see 0.3 Volts AC
5. On the CDI bundle there is a 2
wire connector with a orange wire and a black wire. Slide the meter probes in
beside these wires. This is the CDI output to the ignition coil primary winding.
When the starter is kicked rapidly, you should see 0.4 Volts AC.
If any
of these voltages are missing one of 2 things is happening. Either the source
device is not generating the signal or the destination device is shorted and the
signal is being loaded down. If one of the signals is missing, seperate the
electrical connector for that signal(electrically unload it) and connect your
meter to the source side and repeat the test. Here are the unloaded readings for
the above listed signals
2. Low speed charge coil 50 Volts AC unloaded
3.
High speed charge coil 4.5 Volts AC unloaded
4. Pickup coil 0.3 Volts AC
unloaded
5. CDI output 24 Volts AC unloaded
In the case of signals 2,3 and 4 if the loaded test is bad
and the unloaded test is good do a resistance test of the source device. The low
speed coil (test 2) should read 225 ohms (or 133 ohms depending on engine type).
The high speed coil (test 3) should read 5.3 ohms and the pickup coil (test 4)
should read 115 ohms. If the resistance check is good the CDI is most likley at
fault.
In case the signal 5 load test is bad and the unloaded test is good, measure the resistance of the ignition coil primary winding. The primary winding resistance is around 0.33 ohms. If it is OK then the CDI is most likley at fault.
If all the above readings are good then check the secondary winding of the ignition coil, the measurment from one plug cap to the other should be about 23K ohms. The plug caps themselvs "screw" (twist counterclockwise)off of the plug wires each plug cap should read about 10K ohm when measured by themselvs. The coil and plug wires alone should read 3.5K ohms. It is possible for the coil secondary to be breaking down under high voltage but measure just fine with the ohm meter. If you are getting the proper signal on the black and orange wire to the coil with no spark out into NEW plugs, then the coil is probably at fault. I had this happen intermittently for about a year, I finally found it by connecting up a meter to the black and orange wires and taping it to the tank where I could see it. The next time the bike quit, while I was coasting in gear the input voltage was still there with no spark out, Good in, garbage out. told me it was the coil. One final word of caution. DO NOT ATTEMPT TO MEASURE THE OUTPUT SPARK VOLTAGE FROM THE IGNITION COIL! IT IS 10'S OF THOUSANDS OF VOLTS AND IT WILL DESTROY THE METER!