Aquired a '78 1150 and am in the process of reviving it. Have been reading the forums here for information. We have rebuilt the carbs and fuel pump. When we opened up the distributor cap noticed some dust and clened it out. Replaced the wires. When we started to crank it, we were able to get it to run for a short while. After some trouble shooting we had lost spark. Reopened the distributor and found a lot of dust this time. The brush and spring, in the center of the cap, were gone. All of the dust was the remains of both. Any idea how this happened?