Went out today & had to idle around in the 6 mph zone had to idle back to ramp around a mile at around 2000 rpm everything was runnunig great when the sound of the motor changed lifted then reved it up it just sounded louder that was before, real weird could not run it wide open so got to the ramp & shut it down & it would not restart, got home & pulled some plugs & they were black could have a foulded plug & it dropped a cylinder but I thought this motor would have ran hot enough to keep the plug brown hope I will put in some new plug & do a compression check monday,what should the psi be on this motor?