12V battery ignition with/Automotive coil conversion on 1-Cyl Cast Iron Briggs

Hey guys, I finally got around to working on this old Briggs and Stratton engine, Montgomery Ward Variable Speed 15 that I picked up as a donor tractor for my Gilson, needed a transaxle. Posting here as the issue is the B&S that is common to lots of older garden tractors.

Well, I found another Peerless 2300 series transaxle and decided to get this old thing working. I started to work through the engine to get it working, no spark a few years ago when I picked it up. It turned over by key, but no spark, so it just sat in the back yard, as with no trans, it was of no use but for parts. It has a Briggs and Stratton Single Cyl cast iron engine, I'm guessing 15 hp, Anyway, looks like the original coil bit the dust, and the previous owner cut the wires and installed an automotive coil and switched to 12volt ignition from magneto to prevent having to pull the engine to replace the old coil. New system for me to work on, so after lots of "learnin" on the subject via forums and Youtube, everything tested out as good, or appeared to, and with some adjusting at the points, it finally fires a strong spark. While testing, I left the points/condenser cover off the engine, and while there is a small spark at the points when turning over, there is a big nasty spark as soon as I stop turning over. I haven't put gas in it, still need to clean the carb, but considering the way these Flo-Jet carbs tend to leak, that spark has me concerned. Is that normal? Likely to cause any problem? Once the cover is on, it isn't likely to be a problem with the gas if it leaks, just curious on what I should expect going forward. Thoughts?
Considering white powdery dust came out of the hole when I pulled the high speed needle valve out of the carb bowl....carb will need a thorough cleaning, possible re-built parts, before this thing will run.