LT500R engine no spark

LT500R engine no spark
Posted by Rainman56 on 09 Jan, 2016 12:04
Ok have an lt500 engine with no spark.Cleaned the engine to mounts/frame for good ground coil is good.Changed the pickup/pulse coil as the resistance was over 500 and definitely toast as new one is 235.

The magneto tests good resistance wise but I was told to check the AC voltage for output and am only getting 17 volts AC...been told that's not enough so do anyone know what the source coil output should be?Been told usually min 25 and some upwards of 100.

Wiring is all good so its either the mag or the CDI but if my info is correct seems like the mag is toast as well.
Any info is appreciated thanks.

#1 Reply
Posted by Glamisrider on 09 Jan, 2016 12:51
Quote from: Rainman56 on 09 Jan, 2016 12:04
Ok have an lt500 engine with no spark. Changed the pickup/pulse coil as the resistance was over 500 and definitely toast as new one is 235.

You changed out the main P/U coil and it tested good Ohms before installing it?

Quote from: Rainman56 on 09 Jan, 2016 12:04
The magneto tests good resistance wise but I was told to check the AC voltage for output and am only getting 17 volts AC...been told that's not enough so do anyone know what the source coil output should be?Been told usually min 25 and some upwards of 100.

If your testing A/C volts, since there is no spark, I know the motor is not running, and the 30 RPMs you generating by kicking it over you will not get the same A/C voltage as the bike running at 2K -5K RPM, which is probably where the spec comes from so I would not be so worried about this. If the P/U coil is generating a pluse that's all you need.

It's all a matter of process of elimination and knowing what the most likely causes of the issue are, so here you go:

1st) Make sure your ground on the ignition coil & the ground & the slip fit plug on the rectifier are connected and connected well. I'd also switch to a known good plug just in case. If these all test fine the go to step 2.

2nd) If you have replaced the P/U coil and it tested good resistance (Ohms) before installing it), test it at the harness as there could be a wiring issue between the coil and the harness connectors. In fact test both the P/U coil and the lighting coils at the harness connectors so you know that the entire stator set up including the wiring has no issues all the way to the harness plugs. If the entire stator tests within spec at the harness then move on to step 3

3rd) Ohm test your main ignition coil to make sure the wire connections in the ignition coil are connected and it's working correctly and not compromised. If you not sure with the Ohm meter tsting, change it out with one from a working bike. If that does not fix it, go to step 4.

4th) If the all the stator parts Ohms out ok and the ignition coil is ok, then replace the rectifier with one from a working bike. If I remember right you can not use the Ohm meter to read the rectifier, it just does not work. I've had it read or not read at all but it still work on a working bike so just replace it with a known working one. If that does not fix it go to step 5.

5th) Replace the CDI with one from a working bike as you can not Ohm this out, even though the book gives you readings for it, you can't do it with out a special set up. Just replace it with one from a working bike. If that does not fix it then go to step 6.

6th) The last thing is the flywheel, these have been known to loose there magnetic sections so switch it out with one from a working bike.

You should find a solution at some point in this process.

good luck.

LUK what it was.

#2 Reply
Posted by MotorGeek - Jerry Hall on 09 Jan, 2016 16:53
First replace the spark plug. Then check all wiring connections for cleanliness and tight connections.

!. Check the peak voltage at the feed wire terminal on the ignition coil where the wire from the CDI is connected. (The wire from the CDI must be connected to the coil during this test.) The voltage should be at least 100 volts. If the coil is good it will spark with 60 to 80 volts, but not usually run good under a load. If it is over 100 volts and do not have spark, replace the coil, or plug cap or spark plug wire.

2. If you are not getting any voltage at the feed wire terminal on the coil check the voltage from the source coil coming from the stator with the stator wires disconnected from the wiring harness. The peak voltage should be at least 100 volts. I you do not have at least 100 volts replace the source coil and or wire that connect the source coil to the wiring harness.

3. If you have 100 volts peak coming from the source coil on/from the stator, check the peak voltage coming from the pickup/trigger coil on the stator. It should be at least 1 volt. If you have 100 volts from the source coil and at least 1 volt coming from the pickup, replace the CDI box with a known good one.

4. If you still do not have spark, check the wiring harness for continuity between the connectors.

5. If you still do have spark start over you have missed something.

The above test has worked on anything I have ever tested that has a CDI ignition that is on dirt bikes, quads, jet skis, etc. The above test voltages are also valid for these vehicles.

To measure peak voltage you need an oscilloscope or a digital voltmeter/multimeter with peak voltage capability or a peak voltage adapter that plugs into your voltmeter/multimeter.

If you do not have a peak voltage adapter you can make one for about $2.00. Google how to make a peak voltage adapter.

#3 Reply
Posted by Rainman56 on 09 Jan, 2016 17:35
Thanks motorgeek that's the info I needed.Looks like the stator is gone.Any replacement stators better than others?Rickey stators,etc?

#4 Reply
Posted by Q2W on 11 Jan, 2016 07:38
I've had good luck with my Ricky Stator. Been on my bike for about 10 years with no issues.

Not sure if people were confusing Ricks Stator with Ricky but some people seem to have a lot of issues.

OEM stator will cost about 2 to 3 times as much.

#5 Reply
Posted by Glamisrider on 11 Jan, 2016 11:15
Quote from: MotorGeek on 09 Jan, 2016 16:53
1. Check the peak voltage at the feed wire terminal on the ignition coil where the wire from the CDI is connected. (The wire from the CDI must be connected to the coil during this test.) The voltage should be at least 100 volts. If the coil is good it will spark with 60 to 80 volts, but not usually run good under a load. If it is over 100 volts and do not have spark, replace the coil, or plug cap or spark plug wire.

With the below mentioned "oscilloscope or a digital voltmeter/multimeter with peak voltage capability" the motor DOES or DOES NOT need to be turning over (kicking it) during the test mentioned above?

Quote from: MotorGeek on 09 Jan, 2016 16:53
To measure peak voltage you need an oscilloscope or a digital voltmeter/multimeter with peak voltage capability or a peak voltage adapter that plugs into your voltmeter/multimeter.

If you do not have a peak voltage adapter you can make one for about $2.00. Google how to make a peak voltage adapter.

Thanks

#6 Reply
Posted by Rainman56 on 11 Jan, 2016 15:54
Quote from: Glamisrider on 11 Jan, 2016 11:15
Quote from: MotorGeek on 09 Jan, 2016 16:53
1. Check the peak voltage at the feed wire terminal on the ignition coil where the wire from the CDI is connected. (The wire from the CDI must be connected to the coil during this test.) The voltage should be at least 100 volts. If the coil is good it will spark with 60 to 80 volts, but not usually run good under a load. If it is over 100 volts and do not have spark, replace the coil, or plug cap or spark plug wire.

Need to kick it over with spark plug out.

With the below mentioned "oscilloscope or a digital voltmeter/multimeter with peak voltage capability" the motor DOES or DOES NOT need to be turning over (kicking it) during the test mentioned above?

Quote from: MotorGeek on 09 Jan, 2016 16:53
To measure peak voltage you need an oscilloscope or a digital voltmeter/multimeter with peak voltage capability or a peak voltage adapter that plugs into your voltmeter/multimeter.

If you do not have a peak voltage adapter you can make one for about $2.00. Google how to make a peak voltage adapter.

Thanks

#7 Reply
Posted by MotorGeek - Jerry Hall on 11 Jan, 2016 21:51
Quote from: Glamisrider on 11 Jan, 2016 11:15
Quote from: MotorGeek on 09 Jan, 2016 16:53
1. Check the peak voltage at the feed wire terminal on the ignition coil where the wire from the CDI is connected. (The wire from the CDI must be connected to the coil during this test.) The voltage should be at least 100 volts. If the coil is good it will spark with 60 to 80 volts, but not usually run good under a load. If it is over 100 volts and do not have spark, replace the coil, or plug cap or spark plug wire.

With the below mentioned "oscilloscope or a digital voltmeter/multimeter with peak voltage capability" the motor DOES or DOES NOT need to be turning over (kicking it) during the test mentioned above?

Quote from: MotorGeek on 09 Jan, 2016 16:53
To measure peak voltage you need an oscilloscope or a digital voltmeter/multimeter with peak voltage capability or a peak voltage adapter that plugs into your voltmeter/multimeter.

If you do not have a peak voltage adapter you can make one for about $2.00. Google how to make a peak voltage adapter.

Thanks

The engine has to be turning over at least at cranking speed to conduct the above test. Most dirt bike CDI ignitions need to turn over 400 to 600 RPM to generate enough peak voltage from the stator to charge the capacitor and then trigger the capacitor to release the voltage to the ignition coil.

The test measuring peak voltage simulates what is actually happening when cranking it over to start. Most CID ignitions need to about 100 volts sent to the coil to make enough spark to start. When the engine is running the voltage sent to the coil goes up. Some CDI ignitions will send over 200 volts to the coil at medium to high RPM.

If the coil has a turn ratio of 200 : 1, the spark plug will receive approximately 200 x the input voltage or 100 volts x 200 = 20,000 volts

The pulser or trigger coil needs a pulse of 1 volt or more sent to the CDI to throw the switch that allows the capacitor to discharge the 100 volts or so that it had been storing.