Does unity 5 has issues in light mapping large sets??

Hi guys,
i’m doing a racing game, and the track length is about 2*2 km and the track length is 4-5 km approx. when i try to lightmap the scene , it is taking hours and i’m getting no results.
One solution i found is, scale the set 100 times lesser(0.01) and light map it, after lightmapping is done, reset the size to 1. Everything seems to be fine but, now the real problem i’m facing is with light probes. when i scaling back the set to 1, the light probes remain in the same path where the set used to be in 0.01 scale. As there is no way to move the baked light probe data, i’m stuck there.
What would be the problem??
Does unity 5.0 has issues in lightmapping large sets??
Is anyone facing the same problem??

Followed @KEngelsoft instructions and Thanks to @SpiriTx from unity QA , the exact problem is Setting Indirect resolution.
By default unity sets “Indirect Resolution” to 2 texels per unit which is way tooo high, then i set it to 0.01 and lightmapped it, with out any difference.
Boom!!!
My Work is done…!
Thank you unity…

You should set a sane resolution by assigning a default http://docs.unity3d.com/Manual/LightmapParameters.html that makes sense for your scene.