You're welcome. I was as perplexed as you with the "lack of" detail regarding how and when the fuel solenoid became energized. There is only one other circumstance I can liken YOUR situation to (engine acts like it wants to run when cranking, but dies when key is released from START position). Back in the '40s, '50s, and early '60s,, some automotive engine OEMs employed a "ballast resistor" in the ignition coil circuit. This "ballast resistor" was placed in the ignition coil circuit so that the normal system voltage, was cut by 50% before reaching the ignition coil. This meant that on a vehicle with a 12 volt electrical system, only 6 volts was fed to the ignition coil from the RUN position of the ignition switch. 6 volt systems cut the power to 3 volts. The most compelling reason for having to "rig up" the coil feed this way was due to the woefully inadequate batteries, switches, wiring and other things electrical, of that time. Mainly, it was the "weak" automotive batteries of the time that had to be "compensated for". Here's why: All applications that utilize a battery to power a cranking motor, will experience a dramatic "system voltage drop" throughout the entire electrical system during cranking. The "drop" is caused by the very heavy "current draw", or LOAD, of the starter. The voltage drop causes the ignition coil "sparkability" to diminish significantly. Add to that, a good frosty morning where the battery is cold and even weaker. Factor in further that the starter itself has worn brushes and sticky bushings and you will have so much current draw.....you might not even get a spark out of the coil. Enter the wizards of yesteryear (uhh, maybe they were just engineers). They developed a method to assure good sparks from the coil during cranking. The idea was to use a 6 volt rated ignition coil on a 12 volt system instead of the usual 12 volt rated coil (3 volt coil for 6 volt systems). But how can you do that? Wouldn't a 6 volt coil "burn up" if you powered it with 12 volts? Yes, it would........but not if you feed the normal RUN position power through a "ballast resistor" to reduce 12V to 6V before it reaches the coil. HUH? The "key" to how this arrangement assured dependable starting was in adding a SEPARATE circuit that would "BYPASS" the resistor while the starter was engaged. Bypassing the resistor meant that the ignition coil would be fed a "higher voltage" (in spite of system voltage drop) when cranking, than in normal running mode. After the engine "caught on", the starter was disengaged and the bypass circuit disabled. The current feeding the coil once again flowed through the ballast resistor and the 6 volt rated coil was safe from burning up. It was somewhat common in those days to confront a vehicle that acted similar to this Scag. (It wants to start while cranking, but dies when let go of key.) Most of the time, that particular problem would be due to a failed ballast resistor. But those systems had some other shortcomings. Sometimes you would find a vehicle where the owner would complain of "it just cranks and cranks and cranks, but if you turn the key loose, it might start up at that moment. THIS condition was due to the BYPASS circuit being open for some reason. OEMs accomplished "BYPASS" in different ways. Some added an extra post to the ignition switch that would power the bypass circuit during cranking. Other OEMs added an extra wire to the starter solenoid that powered the bypass circuit during cranking. When something became open in the bypass circuit, the coil would only be fed the reduced voltage. Then you were right back to the situation before the ballast resistor systems came into use. Advances in battery, ignition, starters, and conductors in general, made the use of ballast resistor systems disappear in the 1970s (except for some industrial applications). Oh yeah, magneto ignition systems were unaffected by voltage drop in the vehicle electrical system because they are "self contained spark generators".

Now if you would have took the old coil, and holding it by the spark plug wires, dipped it into a cup of Marvel Mystery Oil, that would have fixed it too...... But now, since the mower is fixed, and the problem was the coil, on the MAGNUM,.... Did he check for voltage on the kill wire circuit, which would have damaged the old coil, and WILL damage the new one? That is the $100 question. Coils do go out, but many times, if not most, they are damaged by stray voltage that gets into the kill wire circuit. Partial voltage damage, then the coil comes and goes out when hot. Full 12 volts, it goes real quick..... That is the question now....... Fish

Update....the engine is running!!! My son and I had faced a setback earlier in the week when one of the head bolts sheared after the second round of torquing to 36 ft-lbs. That was a bummer, but a couple days later we got the bolt out with an easyout. We put all the parts of the rider back together (with a new needle/beam torque wrench) and fired it up with some carb cleaner, and it started up fairly quickly!!! As expected, we did have the smoking of burning off of oil, but after 20 minutes or so, that seem to diminish to nothing. Seem to have a little bit of burning oil smell still, but I am hoping that is just some residual oil burning off the frame or muffler shields - those parts around the muffler seem to get very hot. Only remaining issue was a backfire after turning it off. It happened half the time after shutting it down, even when I would let it idle for 15 seconds before turning it off. But I can probably live with the backfiring. I would welcome any input on this problem, but I can do some research on the internet about this seemingly separate issue. Thanks so much for walking my son and I through our first fix of this magnitude....usually we only fix fuel problems. It was a really satisfying experience, and I am really grateful for your advice along the way....I was truly amazed. Again, thanks so much.

I'm guessing the 2nd one is a 270810? Hopefully, you'll split these 2 machines into 2 separate threads. Things may get quite confusing if talking about similar problems, but 2 machines. Things to do for both- Get the battery charged & load tested. One good battery would probably work for both IF it's KNOWN to be good. Check the fuse! Jumper 12V directly to the small terminal on the starter solenoid. IF the engine cranks, the battery, starter motor & solenoid are good and the problem is between the key switch & solenoid. Report back with the results. On the Kohler,the carb fuel solenoid should click when the key is turned ON. With the key ON, manipulating the seat switch should make BOTH OPR's (Operator Presence Relay) click. Do you have the Owners Manuals? If not the one for the Kohler is - http://www.managemyhome.com/mmh/lis_pdf/OWNM/98120017.pdf IF I guessed the correct model number for the Briggs, it's here- http://www.managemyhome.com/mmh/lis_pdf/OWNM/98100087.pdf IF I didn't, post it so we aren't spinning our wheels over an incorrect schematic.