You ride with the Waianae Mountain Range on one side and the ocean on the other. The trail consists of a mix of jeep road, sandy trail and paved road.
Starting the trail from the Waialua side you leave the dirt parking lot and find yourself on the biggest climb of the entire ride. The climb itself is not too bad but the road is very rocky making it a bit more challenging. At this point the road is very wide and you are likely to see people in their trucks doing a little 4 wheeling.
Eventually you will get to a point where you will have to dismount and lift your bike over some rocks and through a gate. The trail narrows a bit and turns from jeep road into a rocky, more sandy path. At this point you are on the wildlife preserve so please follow the signs and stay on the trail.
Stop at the point for a break or continue on to Yokohama beach. Eventually you will reach a section of the trail that has been completely washed out. Turn around here or backtrack 50 yards to take the trail that will lead you up and over the washout. We have included some pics and a video of the washout to give you a better idea of what you are getting yourself into.
Once over the washout I usually ride to the Satellite Tracking station before turning around.
One thing to keep in mind is that there is zero shade for the entire length of the ride. Ka'ena in Hawaiian actually means, 'the heat'. You will know why once you have ridden the trail. Bring plenty of water, it gets hot.
Also be sure not to leave any valuables in your car. Although there are usually other cars in the parking lot it's a pretty secluded area and I wouldn't want to chance having something stolen.
Clicking on the link above you bring you to Google Maps where directions to the trail are plotted in from Honolulu Airport.
Download the GPX file and use your favorite software to upload trail data to your GPS. Right click on the link and select "Save Link As..." in order to download it.