I have the LA120 42" john Deere riding mower with a strange starting issue, most of the time when I try to start it, hot or cold, it starts to crank then grunts like the ignition timing is too advanced, i continue trying to start it by key cycling until it eventually gets past the hard cranking spot and starts, which drains the battery to the point the charging system does not charge it fully during the mowing cycle and have to trickle charge it for the next time i mow.
What I have tried.
Clean battery terminals and connection points, charge and test battery, its good.
Connect fully charged car battery with jumper cables directly to the starter, same issue.
Replace starter with a new one, exact same issue.
Only workaround I can think of is to install a coil ground kill switch, get the motor spinning then turn on the coil.
Any known issues with this model, maybe a faulty ignition module?
Internet research turns up nothing so far.
Any help is appreciated.