By dirt tracker do you mean it's just going to be flat track racing on dirt?
If I was going to do that I would remove the stator and rotor, the regulator and rectifier. Remove starter and block off where it was. Strip out all the wiring. Use the points, condensers. coils and a kill switch and a battery. With just enough wires to make it run. Charge the battery between races. This is called a total loss system. Most racers build bikes this way. removes lots of weight. And even a small battery will last longer than most races.