Yamaha Grizzly Starter

A customer brought in a Yamaha Grizzly that would not start.  When the start button was pressed nothing happened, not even a click from the solenoid.  The battery voltage checked out ok so I tested the power going to the solenoid coil.  A little probing around with a volt meter showed that the solenoid coil was receiving the start signal, but was not working.  The solenoid would have to be replaced. 

After determining that the solenoid was bad I wanted to check out he rest of the system so I jumped the terminals on the solenoid with a screw driver.  This test (which they actually recommend in the Yamaha service manual) can tell you a lot about the condition of the start system.  There are three possible outcomes of this test.  The most common result is no sparks and no starter movement - means that the brushes are worn out or faulty.  The second result is medium sparks and the starter turns - indicates the starter is fine but the solenoid is faulty.  The last result is lots of sparks but no movement on the starter - indicates that the starter is drawing a high amperage but cannot turn.

I found the last result, lots of sparks but no movement.  The next step is to remove the starter and see what is going on.  The plastic body work on the right side needs to be removed and the air intake hose on the clutch cover.  The first photo shows my hand reaching in to loosen the bolts.

Here is the starter sitting on the work bench.  I make a few reference marks on the motor casing before taking it apart.  These marks make it easy to get the end caps back on in the proper order and in the correct rotation.

Here is the starter with the end caps off.  The magnets are broken and the pieces were jammed in tight and preventing the rotor from turning.  I am not sure why the magnets broke.  One possibility is that the faulty solenoid prevented the starter from operating and someone decided to tap on it to get it going.  On a starter with wore out brushes you can sometimes get it to by giving it a few taps to loosen up the stuck brushes.  A few light taps are ok, but maybe someone pounded on it very hard.