3dsMax Biped always importing with rotation of 270, 90, 0

not sure if it's the same with Bipeds but I had a few issues with scale and rotation when exporting unrigged models from 3DS max.

To solve it I do the following steps to export the model:

In 3ds max set the units scale to metres so 1 unit in 3ds max will be 1 unit in Unity.

set the pivot to align with the default axis in 3ds max, there's a button on the pivot options called something like 'align pivot' or 'reset pivot'. (Sorry not at a computer with 3ds Max on it at the moment) Basically the pivots X axis wants to be facing the same direction as 3ds X axis and so on for the Y and Z axis.

You then want to rotate the objects (make sure the pivot doesn't change) in your 3ds max scene so they face positively down the Z axis and the Y axis is up to match Unity's default settings. Then reset the X-form on all the objects.

Now export the fbx file and import it into Unity.

In Unity, now you've reset the xform the scale should match up, so in the import settings in Unity, seting the 'scale factor' to 1 the models size will now match the size it was in 3ds Max.

If you drag the model into your scene now, the rotation of the X axis on the meshes will be -90 for some reason (don't know why), just set that to 0 and the models will now face down the Z axis properly again and you now have a model that uses Unity's default axis with all the default rotations as 0.

Like I said though not sure how it works for bipeds but I would imagine it should be the same. Then again it might not and I'm just gibbering stuff you already know :)