There is an easy way to make sure you do not screw up the timing when changing the belt. Do the step to line up the marks by turning the motor.Once the marks are lined up take a paint marker and make a mark on the pulley were the notch is and also make a mark on the belt in the same place so they line up. Do this to both cam pulleys and the crank pulley. Also make sure to mark on the belt which mark is for which pulley ( crank ,left cam, right cam). And make sure you know what direction the belt turns. Then you can remove the belt. Take the old belt and count the teeth between the marks on the old belt,and make the same marks on the new belt,you should have the same amount of teeth between the marks on the old belt and the marks on the new belt. It is very important to get this right ,so double check . Install the new belt and line up the correct marks with the correct marks on each pulley and use some spring clips to hold them in place.When changing the belt the important thing is that you get the belt on with the same distance between the marks on the pulleys. You could line up the pulleys perfect with the marks and put the belt on with it one tooth off and you now have the motor out of time.If you mark the belt count the teeth and make sure the correct amount of teeth are between each mark you will only have to do it once. And do not trust the marks that are on the new belt as being correct, mine were not. shawn