The most rideable route would be from Dalwhinnie southwest to Loch Pattack, north the west following the River Pattack, down the side of Lochan na h’earba, NW towards Laggan Dam, S down the strath ossian road to Loch Ossian then from Loch Ossian to Loch Treig (the path running NW from loch bypassing station is better IIRC). That’s all landrover track and reasonably easy going. From Loch Treig it’s about 6km of on/off the bike to Meanach then you can follow the Loch Eilide track to Kinlochleven.
From Kinlochleven could go S over the Devil’s Staircase to Kingshouse, then WHW past Ba Cottage to Loch Tulla, W to Glen Kinglass and SW to Taynuilt – again that’s virtually all rideable – top bit of Devil’s staircase (after you leave the hydro road until A82) would be a bit on/off but rest is fine.
Could go via Lochs Ericht and Pattack to Culra bothy then Bealach Dubh, trackless to Ossian then pick up the route suggested above. Harder, more mountainous but probaly half the distance of the rideable route. EDIT – just realised you’ve done that, d’oh!