It is possible to bypass a starter solenoid on a lawn mower by connecting the positive terminal of the battery directly to the starter motor. This will bypass the need for the solenoid to engage in order to start the engine. However, it is important to note that this should only be done as a last resort, as it can cause damage to the starter motor if not done correctly. Additionally, this method will only work if the problem lies with the solenoid itself and not with the starter motor itself.