Colt Case Ingersoll Garden Tractors

The MTD990 has a cast Iron Briggs with Magnetronic ignition. I don't think its working well. It's missing and I guessing a lack of power. It stalled when I moved forward in the garage. It had sat for 10 yrs. I started it about 3 years ago, but didn't let it run much. So I let it run for 15 minutes to seat the valves. I drove it around the yard, tried adjusting the carb. I couldn't get it to run smooth or low idle. There was no smoke (white or black), so I think engine is in good condition. I have the wrong ignition switch on, so the kill wire is just loose behind engine. When I did shut it down, I held the wire to the engine case and it started running worst and backfiring, but didn't stop. I had to lower the engine speed down and ground wire again to kill it. I think the coil is doing some kind of weird sh*t, arcing where it shouldn't. On another tractor, I had an earlier version of the 16HP B&S with points and flywheel mag that similarly had no power; I changed it to a automotive coil and it worked great from then on. I going to clean the carb to rule that out, then I will set it to work roto-tilling to evaluate the power, or re-break-it-in.

Your experience would be appreciated!

Where's the coil arcing?

Well, just to finish this post; It's working okay now. As usual I did several things at same time so can't pinpoint. Neighbour offered to clean carb at work in ultra sonic cleaner. It was gone for 5 days, so I replaced key switch. I was a little impatient, so I used carb off another tractor. Starts and stops with key now. Works at idle in garden, so no power concerns. Still misses a little; maybe that how these run?

Well, just to finish this post; It's working okay now. As usual I did several things at same time so can't pinpoint. Neighbour offered to clean carb at work in ultra sonic cleaner. It was gone for 5 days, so I replaced key switch. I was a little impatient, so I used carb off another tractor. Starts and stops with key now. Works at idle in garden, so no power concerns. Still misses a little; maybe that how these run?

I would doubt that it's normal to "miss a little"

Either the ignition is still a problem or the old carb is dirty, vac leak at shaft or out of adjustment .