the YouTube compression they use is way to much for some videos and makes them unviewable.
You can upload the original file to kitewatch.com so it can be downloaded.

If file size is Very Big let me know What it is and the bit rate of the original file ?
Anything over 10Mb per minute is way over the top for web viewing.
anything under 512Kb/s gets blocky when viewed Full Screen
Alan - Kitewatch.com