BMW make a real dirt bike?

This weekend I went to see the BMW X-challenge. Ok so this is a big bore machine but it is listed with an unladen wight of 156kg which makes it significantly lighter than the old F650 which weighs in at 191kg unladen. Quite where the 35kg have been saved as anybody's guess. A little bit everywhere I suspect. For comparison the Alp 4.0 is listed at 133kg dry. I'll put it on the scales sometime, but you could assume 10l of fuel and oil add at least 10kg.