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P.J., Technician
Category: Motorcycle
Satisfied Customers: 750
Experience:  10 years as a mechanic and fabricator in a privately owned, local, custom bike shop.
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I have a 2002 sportster it ran a few weeks ago and now it

Customer Question

I have a 2002 sportster it ran a few weeks ago and now it wont start. I did a spark test and I have one spark then nothing. Could this be a coil? What other tests can I do?
Submitted: 2 years ago.
Category: Motorcycle
Expert:  P.J. replied 2 years ago.
Though it is possible I'd suspect the coil last. They very rarely go bad.
If the single spark seems to always come once as soon as you let off the start button then you can just about count on a low voltage problem causing your issue. When cranking, the voltage can be dropped to a point below 10 volts which is really the lower limit for the ignition system to produce a spark. If you have a voltmeter that can record low and high voltages then you can connect it and record while cranking to see what your voltages are. Check the voltage first and eliminate it as the problem. You can also have your battery load tested to see if it is good as well as checking your cables for clean and tight connections.
The next check is also a simple one and that is the spark plugs. If they look black from soot then they may be fouled. If you used your plugs for the spark test then try a new set or a spark tester to see if the results are the same. No need to try to clean fouled plugs as they are nearly impossible to bring back to life.
There are other possibilities for sure but these two are the most common and should be eliminated first.
Let me know what you find and we can continue if need be.
Thanks, P.J.
Customer: replied 2 years ago.
I have good voltage. The only spark is when you first start cracking. The plugs didn't look to bad. I did a spark test and got the came result just one spark when you start cranking
Expert:  P.J. replied 2 years ago.
Ok. If you're confident that the voltage stays above 10 at all times and the plugs are good then there you are pretty well limited to testing connections.
You cannot test the ignition module without specialized equipment and cannot test many functions without a breakout box.
Do you have a volt/ohm meter for a couple other tests?
Customer: replied 2 years ago.
Yea I have a fluke
Expert:  P.J. replied 2 years ago.
Okay, and do you know what specific model 1200 you have?
Customer: replied 2 years ago.
It's just a standard 1200 sportster
Expert:  P.J. replied 2 years ago.
Okay, bummer, the 1200S (Sport) has some built in diagnostics but the Standard doesn't.
I'm going to get together some troubleshooting flow charts for you. I'll send them your way in a few minutes.
Expert:  P.J. replied 2 years ago.
Alright, below is a link to the troubleshooting section that covers your bike (and other models as well). At the end I've included the wiring diagram for your specific model. I don't have the HD manual with me on my computer but this manual information is pretty good even though it covers quite a few years. Many tests are the same no matter which model you have.
As I mentioned earlier, there is going to be some stuff you can check and some stuff you cannot.
Begin with the easy stuff, such as simply checking the connections to everything just to make sure they are clean and tight. Your bike has pretty good plugs on it but anything can happen. Wiring can get bent and broken and terminal ends can get loose.
The coil tests and plug wires tests are very quick and easy with your meter.
Other simple tests are for voltage and ground at the proper locations on the ignition module and coil.
Please let me know if I can be of further assistance.
Thanks, P.J.