I have a total new rebuild and my question is, when I put the stator plate back on I line up the marks with the plate and the motor block. The sled runs fine but now and then comming down from a hard throttle I get a slight back fire I have heard of people checking thier timming with a light is this to fine tune it or is the way I did it the right way and I should look for the cause some where else? I checked the marks on the stator and block and they are still dead on but i never marked where they were when I took it off. ??? If I need to use the light please explain how