@CloudyMrs train to Garve. Cycle to Achnasheen, down the side of Loch Maree to Gairloch, on to Poolewe (stopping for coffee and cake from the caravan), through Camasnagaul (great name eh, and look out for feral goats) to Braemore Junction, and turn right past Loch Glascarnoch back to Garve.
That's a bit over 100 miles so if you want to extend it then turn left at Braemore Junction and pop down to Ullapool and then come back. That'll add another 25 miles or so.
Hope that's far enough?