vibrations are the charateristic of RTR"s engine....................
the sound that comes with it,and then tacho goin skywards are the trics it's engine plays...........
you'll get them the most at around 5000-6500RPM........
not to worry and ignore em,as post that rpm range you'll be gettin the pull which will make you smile till the magic 12000 RPM.......
MAn it's the most "puttin the smile on the face" engine i came across...............