A very tough, rough route exists from the southern end of Takapari Rd to the Otamaraho Stream on the eastern side of the Ruahines, for onwards access to Kumeti and points South.
From the end of the 4WD Takapari Road, continue south along the tops on an overgrown, but followable tramping track. This is shown on maps, continuing a further 1.5km along the eastern escarpment. At the point where the map shows the track stopping, a roughly cut track swings SW towards the spur north of the Otamaraho Stream. JJust befor the drop-off, the track forks, the northern fork dropping into a slip at the head of the the next stream north, and the southern fork heading for the spur. The track is reasonably well cut (2014) for the first 100 vertical meters descent, but beyond that becomes very overgrown. Occasional tape, tin lids and old cut stumps are all the indicates that a track was every present. It is possible to bush bash down the spur until it flattens a little and bush gives was to tall toetoe mixed with waits to head high scrub. Here progress becomes very tricky, and I dropped off the spur, heading SSW. I do not that on air-photos (WAMS), a bov of some sort seems to exist another 400m down the spur,so if you persist, you may pick up a track leading to that - but I found the way impassable once I hit the toetoe.
Initally, going dropping off the spur continues very scrubby and tight, but once below the scrub, heading SSW off the spur, the bush became open and going good for about 100 vertical meters, following a small sidestream visible as a dry gully on the map. 60m above the Otamaraho valley floor this creek met waterfalls and vertical faces. DO NOT CONTINUE below this point, instead, sidle upstream (WNW) onto good, if steep slips which can be descended to the valley.
From here it is a simple process of following the Otamaraho downstream. A couple of small waterfalls in the first 150m require scrambling round, but once below them, the valley floor is broad and flat as far as the park boundary.
Outside the park, a Queen's Chain exists, so you could continue down the creek if you wanted, to Thornburn Road. Alternatively a reasonable, but steep route crosses the spur to the SW, just inside the park, to the Kumeti roadend.