Yup what Maddog said. Could be the gap though. I had the same problem on a SPE 26 I bught a couple years back that had been converted by the dealer to Rcexl. The gap was such that it would start, but then would die after 20 to 30 seconds. It would not restart until it cooled down. Turned out the gap was just at the point it would fire and as soon as it started to warm up the gap would increase just enough to make it stop. Took quite a while to figure it out and solve. Once I reduced the gap it ran properly.