Motorcycle Questions? Ask a Mechanic.
HI and thank you for your question.
The first thing I suggest checking is the battery cable connections at the battery, the + cable from the battery to the starter relay and the cable from the starter relay to the starter motor. Then check the (-) battery cable at the battery and chassis ground both. Also notice if there are any signs of corrosion. You might even go so far as to take the cable off the chassis ground and clean it up to be sure you are getting a good ground.
The next thing I suggest you do is what is called a voltage drop test. Connect a volt meter across the battery and set it to read DCV. With the volt meter still connected and turned on, crank the bike and observe the voltage on the meter as the bike cranks. It should not drop any more than 1 ~1.5 volts. If it drops more than that, either the battery has failed or the starter motor has.
If the battery passes a load test, you are going to need to remove the starter and take it apart for an inspection. Mainly you would be looking at the brushes and communtator for signs of wear or failure.
Let me know what you find.
Fair enough. As soon as you have new info feel free to post back to this thread. I'll be here.