Our recent camping trip on our Royal Enfield's took us through some winding blacktop to begin with, up Greenhill Rd, through Summertown, Cherryville, down Corkscrew rd Castambul, through the Gorge, then back past Lobethal, up to Mount Torrens, where we hit around 30kms of dirt road. The dirt starts out boring at first, but when you hit Rolland and Kubenk roads, that all changes up into sandy, rocky, gnarly 4wd track with awesome rural landscapes. Basically a fire track. Just go fast on the sand to stay upright!! Good for dirt bikes, gnarly on road bikes. Campsite is awesome. Remember to clean up after yourself.
This route starts at the old Mount Barker servo on the corner of Adelaide Rd & Morphett St, heads out to Callington via dirt on Back Callington rd (loose gravel with some steep sections), then a quick cross over the freeway to Salem on blacktop, then it's basically all dirt (except for a few small connecting sections) on the way through Red Creek, the back of Bugle Ranges (Red Gum rd looks like a hiking track - Don't be mistaken) and Flaxley, Green Hills and a nice run across Hack Range Rd and Ironstone Rd before hitting blacktop once again on Hawthorn Rd back into Mt Barker. Mostly dirt roads, good in the dry, not sure in the wet.