only certain one have that problem.if it has a pre-set rpm..some will run away. if it has a throttle,it is easy to control and runs very good.....they got that reputation from a batch that was sold on the internet about 8 years ago.boy could they reach a high rpm real quick..even after the problem was discovered, they kept selling them.I have had both and still have one with the adjustable throttle and it is a very nice running engine..sid