My son's 2011 110cc TauTau won't start, and the battery isn't the problem. How can I tell if it's the starter or the relay? And how easy is it to change either of those?

 

So what exactly are the symptoms? Does the starter motor turn at normal speed but the quad isn't starting. If so do you have spark?

If the starter motor doesn't turn, do you hear the starter relay go click when you press the start button? Are you applying the brake before attempting to start? Look at the brake light. Is it lit up when you are attempting to start?

How do you know the battery is good? Have you used a pair of jumper cables to jump your quad battery to your car battery (use extra care to make sure you get the polarity correct)? That's a really good way to figure out if your battery voltage is collapsing under the heavy load from the starter motor. If it cranks fine with jumper cables connected to your car battery then your quad battery is bad or discharged.

Have you done any voltmeter measurements?

 

I did jump it off the car a few times and that worked, and I did put a volt meter on it and it reads 12 volts. It now makes a clicking noise when I try to start it.

 

I dropped the ball on this post. Sorry about that.

Does it make a a clicking noise even when you have it jumped to your car battery? Or does it click only when running off your quad battery?

When you're measuring the voltage on the battery it *must* be done while the solenoid is "clicked" in so the battery is connected to the starter motor. Did you do this?

You must measure the battery under full load or the results are meaningless. Try this thought experiment: Imagine a little 9 volt transistor battery. You measure its voltage and it read 9 volts. Now wire the little 9 volt battery directly to your starter motor. Obviously it won't be able to turn the starter motor at all - it's too little - and if you measured the 9 volt battery voltage while it is wired directly to the starter you would read near zero volts. The battery voltage collapses under the tremendous load of the starter motor.

So you need to measure the voltage at the battery while it's loaded with the starter motor to see if the battery is up to the task.