It seems the pilot in our gas furnace doesn't reliably ignite the main
burner. The upshot is that sometimes, say 1 in 4, the furnace will start
with a real boom. The furnace is regularly serviced and works fine apart
from the starting issue, I explain the problem to the tech's and they take
the burner out, look at it but don't seem to fix it. Any suggestions.

Thanks,

Peter