drat first thing first, put loctite on all the screws that thread into metal. Loose screws can cause a world of trouble. Never allow the rear tires to spin with out a load! (on the ground) Next you want to check for air leaks, check the base of the carb, fuel lines, make sure the head is tight. Once you check all this set the needles back to the factory break in settings and try to start her up. The way grampi said to break it in is probley the best way to do it. As far as the spur gear check your gear mesh, also make sure the drive line all moves freely. Hope this helps, if you need any more help just ask. Where in ohio are you????