One sounds like a proper bike...the other like a fart in a tin can!
http://www.youtube.com/watch?v=1g0Ub2u4q4I
Then there are these...not sure what they are but they sound great even if you could roast a chicken inside one!
http://www.youtube.com/watch?v=0Mb5M6X5DYI&feature=related
Nutter!!!
http://www.youtube.com/watch?v=qnNaQsQgONI&feature=related