Introduction
This guide gives instructions on removing the side brush motor in the Roomba 870. There are a lot of screws that need to be taken out to replace the motor, so make sure you set aside a spot for the screws so that they are not lost.
Tools
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            Turn the Roomba over so that the back side is facing up. 
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            Using the Phillips #00 screwdriver, remove the 4.0mm screw in the center of the yellow side brush and lift the part out. 
 
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            Use the Phillips #00 screwdriver to remove the four 3.5mm screws that hold down the battery panel and rear panel. 
 
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            First remove the battery panel, which is the small rectangular. 
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            After removing the battery panel, remove the rear panel. 
 
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            Remove the three small 3.5mm screws fastened to the motor housing. 
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            After removing the screws, remove the motor housing from the rest of the Roomba. 
 
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            Remove the 2.5mm screw in the center of the motor housing using a Tri-Wing Y1 screwdriver. 
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            After removing the screw, remove the top shell casing of the motor housing. Underneath, you will see a white gear with two screws next to it. 
 
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            Remove the two 2.5mm screws in the inner motor housing using a Phillips #00 screwdriver. 
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            After removing the two screws, the motor will slide right out the back, and it can be replaced. 
 
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To reassemble your device, follow these instructions in reverse order.