I bought a used revo and having a problem getting to to stay running. It keeps fouling plugs out and just doesnt want to stay running. I took the cooling head off and there are small scratches in it not sure if this motor is toast? When I get it to run it runs ok but just wont run for long then fouls the plugs out. I got it cheap so buy a new motor wont bother me much but i hope this is normal wear and tear. Below is the pick of the bottom of the cooling head I have not taken the rest of the motor apart yet.