I use to own a 150cc motorcycle (don't remember if it was yamaho or suzuki)...dh bought it for me for my 30th birthday...the brake handle was hard to squeeze and I forgot about the foot brake...crashed into a tree... it also through a rod... ;( oh that was the ping ping ping we heard when we bought it... nope not normal for motorcycles (as we were told by the seller) or any engine...we went to automotive repair school in 1994...yup can rebuild engines now...don't have a shop and outdoors is NOT the place to open up an engine :>