I have been using the Yammi stuff since new and havent had any issue what so ever. No fouled plugs limited smoke, etc so its not a performance issue. Its just the fact that is easier for me to get the XD-50 and I alos heard that the XD-50 is actually a better oil.
The XD-50 oil is a blend, and will work just fine in your Yammie, you should be able to get it bulk at your dealer for near $15.00 a gallon if you bring your own container.