Cross Myanmar Burma late April 2015 (From Thailand to India)
 

As the name suggests we (3x 250cc motorbikes) plan to cross Myanmar (Burma) late April 2015. We have visas but no guide or permission yet. If anyone is doing anything similar at a similar time (a week or two either way) let us know if you want to split costs. We will be going from Thailand to India.

We hoped to do Kawthoung to Moreh but will take whatever we can get.

I just returned from Myanmar two weeks ago, entering via Kawthoung. The Kawthoung border crossing definitely has no transport options for cars (I checked as I thought it would be cool to enter here on a future overland trip).
Motorcycles might be doable if they fit in the current passenger canoes that they have shuttling across the river. The road from Kawthoung to Myek is hell. At Kawthoung, they tell you the road is closed and try to force you to take an expensive speedboat. Further North, the standard road entry option is from Tak, Thailand west to Mai Sot (or Mai something) and then to Hpa-An where the road continues to Yangon.
I do believe that to bring your own vehicle, you need to book a Special guided tour (i.e. like China) and it wasn't cheap. I had the name of an organizer but can' t find it at the moment. Also check Lonely Planet.
Good Luck