In The Shop: Starting Issues

We have a lot of questions come in to us concerning starting issues on older, Evolution model, Harley Davidsons. Not only do we see a lot of these questions on the website, but we frequently have these jobs In The Shop. Although there are a large number of issues that will keep a bike from starting, we thought we would take a minute to go over the basic diagnosing process we use when there is not an obvious problem staring right at us.

There are four things that are very important to have before you start. You need a test light, a multimeter, clean and secure battery cables, and a known good battery that is fully charged. If the battery that is being used is in question, it should be taken to a local bike shop or garage so it can be load tested with a professional’s battery load test meter.

Always start by testing for the battery’s static voltage reading. With the ignition switch OFF, set the multimeter to DC voltage. Hold the red meter lead to the battery’s positive terminal and the black lead to the negative terminal. The reading you get is considered to be the battery’s STATIC voltage. It is important to take note of this result as it will be a benchmark for the following tests. A healthy battery should have a static voltage reading somewhere between 12.50 and 14.80 volts.

Now, continue holding the test leads on the battery terminals and switch ON the ignition switch. The DC voltage reading should drop down as the battery is now powering a number of components. Typically, the voltage should not drop more than one full volt with a healthy battery. For instance; if the static voltage reading was 12.70 volts DC, the reading should not drop lower than 11.70 DCV when the ignition is switched ON. If the voltage does drop more than 1 VDC, there may be an issue with the starter absorbing the voltage. Next, pull the small “trigger” wire from the starter. This is usually a green or tan wire with a 90° spade connector and it originates from the starter relay.

Push the red meter lead into the end of the trigger wire and the black lead to the battery’s negative post. Now, with the ignition switch ON and the RUN/OFF switch to RUN, press and hold down the START button. Note the voltage reading. It should not drop more than 1 volt DC from the battery’s current static voltage. If it does, there might be an issue with the starter relay, start switch, run switch, or any of the related wiring or pin & socket connectors up stream.

Moving on to the starter relay.
Inspect for possible corrosion. It is critical for these terminals to be clean and secure especially the ground wire. The starter relay terminals are numbered.
#30 – red wire = constant voltage
#85 – black wire = ground
#86 – black wire with a red tracer = trigger wire from start button, to the starter relay.
#87 – trigger wire from relay to starter.

Unplug the starter relay & starter trigger wire, turn ON the ignition switch, and switch to RUN. Push the red meter lead into #30 allocation and black lead to the negative battery terminal. The voltage reading should be close to the static reading without much of a drop. Move the red meter lead to #86 allocation. Depress & hold the start button. Voltage should not drop more than 1 VDC. Plug the relay back in and move the red meter lead to #87 terminal. With the starter trigger wire still unplugged, depress & hold the start button. The result should be the same or close to the previous test result. Next, set the multimeter to continuity. With the black test lead on the battery negative terminal, touch the red test lead to relay terminal #85. You should have continuity to ground. It is important to visibly inspect the relay ground connection to the frame. If it is damaged, weak, or corroded, the ground should be cleaned and repaired.

Next, it is important to test the voltage going to the RUN/OFF switch. Use the multimeter to test the gray or tan wire that powers the switch. The reading should be close to static voltage. Next, with the starter trigger wire still unplugged, depress and hold the start button. Once again, test the voltage of the black wire with red tracer at every junction that is accessible starting at the switch itself.

There are a great number of wiring and electrical issues that can interrupt the starting circuit of your Harley. These are just a handful of preliminary tests that we suggest to help diagnose or gather clues for an eventual diagnosis.

Must Watch Videos on Topic:

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You have to watch all the videos in this multi-hour project series:

Electrical Systems

Check our Q&A on the topic as well:

Starting Problems
Starter Problems
Discussion
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2 Responses to “In The Shop: Starting Issues”
  1. Tim Mankin
    Tim Mankin

    I have an error code U1255, possible is missing instruction. will that stop a motorcycle from starting?

    Reply