Hi Mike
The 13B etc is just the model of the actual mower and not the model of the engine which will be made by another company ie briggs & stratton etc so its impossible to answer without knowing the type of engine we are dealing with.
mowerguru
September 2009
Automatic Answer
While you wait for answers, we may have found some information which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lawn mowers.