How to trouble shoot your dirt bike electrical system.

A closer look at your electrical system
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Sandblaster
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How to trouble shoot your dirt bike electrical system.

Post by Sandblaster » Mon Oct 08, 2012 7:08 am

How to trouble shoot your dirt bike electrical system.
We receive several emails every week asking about electrical systems.
The most common questions asked:
"I have no spark, how can I find out what is wrong?"
"How do I know if I'm getting any spark?"
"My spark is really weak, what is wrong?"
Most modern dirt bikes have the following electrical components:
Spark plug - Wires - Kill Switch - Coil - CDI - Stator - Fly wheel - pulse generator.
Some have a few more such as a condenser, regulator,
What should you check first?
Do you have a manual for your dirt bike?
If not, get one.
Your bike may require specialized information not covered here.
Also, I caught a bike on fire once because the spark plug lit off some fuel that had spilled earlier in the day, so..... Be careful!!!
Drain the fuel if required, empty the carb, remove the tank, what ever it takes to make it safe.
Always start with the cheapest and simplest things first:

Replace the spark plug.
What does a new plug cost $4-10?
Not much.
Before installing the plug, be sure to check your manual for the proper gap.
As an example the 02 CR250 Honda uses a plug gap is .020-.024".
Also, check for any water in the cap as this is a dead giveaway for a problem.
Still no spark?

Make sure that the coil wire is touching the inner metal plug wire ring.
Before I install the plug I connect it to the coil, hold the electrode to the side of the cylinder, and kick the bike over.
Very Important DO NOT Kick the bike over unless the electrode is touching the cylinder or you can damage your CDI and potentially give yourself another problem to deal with.
Still no spark?

Check the kill switch.
You would be shocked how many times a 20 dollar switch kept a bike worth a few thousand from running.
You can test the switch with your ohm meter.
If you don't have one you can pick up a ohm meter from Radio Shack starting at about 20 dollars.
NOTE: Not all OHM meters have the same internal impedance values.
Just a quick note on impedance, impedance measures how easily a circuit conducts current when a voltage runs through it.
You measure impedance in ohms.
What this measurement tells you is how much of the voltage put into one end will make it to the other end.
The higher the resistance value is, the less voltage is making it through the circuit and usually meaning that something is getting hot :geek:
Your manual may or may not have those values recorded.
If the manual does not say what the impedance value should be they typically tell you what the part number for the correct OHM meter is.
Keep in mind that the impedance values will not make any difference for checking continuity, however, it will make a difference for checking resistance values.
Confused? Yeah, me too :D
Set the ohm meter to check continuity and hold one lead to one wire and one lead to the other wire.
Have a friend push the button.
If your ohm meter beeps the switch is good.
If you don't have a ohm meter you can disconnect the kill switch.
Some caution is in order because with the the kill switch disconnected you will not be able to easily stop your engine if it starts and decides to rev up to 25,000 RPM :shock:
If the bike suddenly starts you can either quickly reconnect the kill switch or pull the spark plug wire off.
Once the kill switch is disconnected, kick the bike over again.
Still no spark?

Check all the wires for continuity and connectivity.
Pull the connectors apart and look for loose or corroded terminals, clean and or replace as required.
Some guys solder all their connections together to eliminate the possibility of a problem.
Others simply replace all the connectors with something a little more robust.
Get your ohm meter out and check all the wires for continuity.
While doing this, carefully check each wire for breaks or damage.
If you find anything that is not 100%, repair or replace as required.
Still no spark?

Check and or Replace the coil with wire and cap.
Did you just paint or powder coat the frame?
Make sure that the coil is properly grounded.
You may need to remove some paint.
In your manual it will have the resistance values for the primary and secondary leads.
You need those resistance values to properly check your coil.
Also, when checking your coil, do it attached to the bike and make sure that it is grounding properly.
As stated earlier, many times the coil wire is not touching the inner metal plug wire ring.
If the coil passes a continuity check you will need to get the resistance and peak voltage values as outlined in your manual and verify that yours are correct.
Another trick guys use on older bikes is to run the coil ground directly to the engine.
Sometimes the frame to engine connections loose the ability to pass ground and the frames don't always have enough area to make a good ground.
If the numbers are all within spec and you still have no spark....

Check and or Replace the stator.
Stators are typically very expensive and you should never order a new one unless you know for sure that yours is dead.
Remember, most dealerships go by this simple rule.
You bought it, don't bring it back.......
Referring to your manual, you will need the resistance values to your specific bike.
Without those values you can't properly check your stator.
Some will say that they can check the continuity and that is good enough.
I respectfully disagree, you need the resistance values.
A stator coil can have great continuity and be so far out of spec (Too little or too much resistance) that it will never spark effectively.
To check the stator you will need to disconnect it from the CDI.
However, a good practice is to leave the stator attached to the engine so that you can be sure that it is properly grounded.
Is your stator in spec but still no spark?

Check and or Replace the CDI
Once again, you will need the specs from your book to check it, that's providing the specs are available.
For many bikes you will get a note in your manual explaining that you can't check the values.
Here is a bit from a Kawasaki manual:
"The I.C. Igniter can only be tested with special electrical equipment and improper testing may damage it. Refer all testing to a Kawasaki dealer".
If your manual has the specs then GREAT! Test it according to their specs.
If not you might want to look at one last thing before you go out and spend some hard earned cash.

Fly wheel inspection
To inspect the fly wheel you will need to remove it.
To see what is required for removing your fly wheel, please refer to this article:
viewtopic.php?f=40&t=118
When you get the fly wheel off the first thing to look at is the key.
If the key is sheared you will need to replace it.
Next, Inspect the fly wheel for loose or cracked magnets and replace if required..

If all of that looks and tests great but still no spark, take all the pieces down to your nearest bike dealer and ask them to test those components.
Remember, if you go out and spend a bunch of money on electrical parts and then you find something else wrong, they won't let you take electrical parts back.

I hope you find this article helpful.
If there is anything that you would like to add, feel free to post or email me.
Thanks!
SB
If bikes are for kids I'll never grow up.

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