A line striper (10) is provided with a relatively small engine (16) operating a reciprocating piston pump (20) and having a centrifugal clutch (18) which actuates when a predetermined engine speed has been reached. A pressure bypass device (22) which opens at either a fixed or adjustable pressure is provided to bleed off excess pressure and maintain a consistent spraying pressure. A double acting trigger (30) is provided for the operator to actuate the spray gun (40) and raise the engine speed simultaneously.