The following Starter Rebuild tech tips are applicable to most ATV's.
Two types of brushes will cover most to the ATV starter motors out there. 2 brush or 4 brush for Denso starter motors and 2 brush or 4 brush for Mitsuba starter motors. Be sure to know who manufactured the starter you are working on (Denso or Mitsuba). This information, along with the starter ID#, can usally be found on the starter motor end cap.
Start by removing the bolts holding on the starter motor reduction gear cover. Witht he cover removed, the upper and lower set of reduction gears can be removed (if applicable). Remove the nut from the terminal stud. Then loosen and remove the bolts holding the starter motor to the crankcase. Wiggle the starter motor to break the seal tension and remove the motor from the case.
Now, remove the long starter motor case bolts and you're ready to remove the brush cap from the case. If the brushes are worn out, the case will be full of powdered brush material. With the shortening of the brushes, the spring tension holding them against the communtator will decrease to a point causing electrical arching.
Next, remove the positive (+) brush and terminal from the starter brush cap. Make sure you keep the order of the washers straight, this will be important during re-installation. When removing brushes from the brush holder, use needle nose pliers to help position the flat spring allowing removal of the brush. If the spring slips off, it usually requires some force to replace.
Before installing new brushes, make sure all of the copper contacts of the commentator are clean. The easiest way to do this is gently abrade away the burnt coating with a thin strip of emory cloth and a little WD-40 for lubrication. Make sure you remove material evenly from top to bottom and remove no more material than necessary.
Now you're ready to install new N2® replacement brushes for your particular application. Measure the lead length of the factory leads on the brushes and cut your replacement brushes to the same length. Flux them and "tin" with solder.
Next, solder the tinned lead to the brush plate. The negative (-) is usually attached to the brush holder plate and the positive (+) to the terminal stud. The positive (+) lead needs to have a piece of woven insulating sleeve placed over the lead prior to soldering it on the positive (+) terminal stud.
Place the brushes in the slots so that the curve of the brush corresponds to the curve of the armature, and then slide the spring back into position. Slide the positive (+) terminal stud carefully into the brush cap then replace ALL the fiber washers previously removed in the exact reverse order of removal. Now, slide the brushes up into their slots and insert the armature.
With the armature installed you are ready to install the rest of the starter case. Align the indicator marks when assembling the center case and end cap. Insert the long case screws and tighten evenly until the rubber sealing O-ring is snug. With the starter motor assembled, it should be tested before reinstalling it in the motor cases. Use a charged battery and jumper cables. Attach the negative (-) to the starter mounting ear and the positive (+) is just touched to the positive (+) terminal stud. If everything was assembled correctly, the starter motor should torgue strongly in your hand and spin rapidly.
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