2007-2009 Honda TRX300EX TRX300X service manual, Page 333Get this manual
ELECTRIC STARTER Coat new O-ring with engine oil and install it in the starter motor groove
INSTALLATION
Install the starter motor onto the crankcaseInstall the ground cable (instal onto rear side bolt) and mounting bolts, and tighten the bolts
Connect th starter motor cable to the starter motor in parallel as shown