The "Cajon del Maipo" valley east of Santiago is quite nice, should be warm enough to explore a bit higher up by October.
I would obviously do Viña and Valparaiso, take the smaller roads, you can avoid all tolls and therefore all boring motorways, a bit tricky, but worth it for the ride.
The trip over to Mendoza is pretty awesome, but make sure you pick the right weather for it, you don't want to get snowed in on a m.c. at 5000m.
The valleys further north will be great in October, there is a great trip you can do which parallels the Panamerican highway to the East and you can get several of the Valleys in, very popular with the small legion of Chilean riders, it will take you through Combarbala, Monte Patria, Ovalle, Vicuña and even up to Pisco Elqui. 150 odd kms East of Vicuña there are some pretty cool thermal baths where you can hang out in the middle of the Andes with a spectacular view of the snow capped mountains, great ride up and you won't see a soul, not many locals know about it.
Have fun, but take care of your bike, Chileans will not bat an eyelid at putting your bike on the back of a truck.