Welcome to the forums. On the Fourtrax 300, one of the lines should have a "F" by it and the other line should have a "T" beside it. You should use the one with the "T". If for some reason, it don't have the "F" and "T", then it should be the second line if you're turning the engine clockwise. If you're still confused, pull the sparkplug out and stick a straw down onto the top of the piston. Now slowly turn the engine over and when the straw comes up as high as it can and before it starts to drop down, that is TDC. When it's on TDC, the correct line will be lined up with the mark on the case.i have a 1991 honda 300 4x4 i just put in new ho pho valve in and ho pho valve ex . i need know how to time it and it haves 2 lines one with 2 dots and the other just a line.need help bad its giveing me a headack.thanks.