The RV150 is a Chinese copy of a Briggs and Stratton, but unfortunately they copied everything but the quality........
The starter unit is a notorious weak l point. If there are no broken parts, you CAN re-assemble it, but you will probably find that the spring has snapped. How old is it? If it's under a year old, return it under warrenty. If not, yoo have a straight choice - order the spring from a Mountfield dealer and wait ages, or buy a complete assembly - about £28.
If you go the spring route, it will be supplied 'pre-wound', and easy to install. If you have one that has 'let go' it IS possible to wrestle it back in with care, but it's an aquired technique, and CARE is required to avoid injury.
phil_saunders@bigfoot.com
Phil Saunders
September 2008