Check out specification number 24539 and 24685. they are two of the M18 engines that were used on the deines mowers.
I know the model number tag was a sticker and is long gone. If the new coil is mounted with the correct side up (yes people put them on upside down), the mounting surface for the coil is clean and the wire is disconnected and the plugs are grounded well it should spark. Depending on type of spark tester you may not be able to get a spark through the tester and the plug, especially if the plugs are not mounted. Just too much resistance for the spark to jump the gap.
I cleaned and reinstalled one cylinder head and a new sparkplug. Hooked plug wire up and jumper cable to starter. Squirted a little gas but engine refused to fire at all. I put the other head back on, new plug & wire hooked up. With compression on both ends it spins a little faster with the starter. Small squirt of gas into each intake hole and each cylinder will now fire. More promising now. Intake manifold will go on next then clean the carb and put it on. I still want to pull the flywheel while this engine is on the bench. Maybe then it will run longer before it needs attention next time.
New intake gaskets, new Carb, installed Temporary gas tank hooked up. Engine runs very nicely. Powerwashed cowling parts and hopefully get it ready to reinstall in mower soon. I found a used snowblower attachment the right width for this mower if I put narrower tires on it. Excited with the thought of it being useful more than one season. And hydrostatic drive means unless the snow is higher than the top of the snowblower it should be able to handle whatever comes. I need to find some 4.80 x 4 x 8, 5 bolt boat trailer wheels to make it narrow enough. Right now it has big fat tires on it.
Well I got the engine back into the machine. Some of the wiring I can figure out but the previous owner took them apart without labeling them. Color schematics in the manual dont match up either. Anyway because the engine creates its own electric for ignition I just took the hot wire that goes to the switch and crossed it to the start wire on the solenoid. As soon as the gas got to the Carb it fired right up. I got to drive it around some. Started looking things over closer and discovered very low oil in the hydraulic drive system. Added to that and drove it around a while to see if there was anything else needing attention. Im thinkin there is a dry bearing in the mower deck somewhere as it seems to turn quite hard. Maybe address that in the spring. Got new narrow wheels, tires and Chains for the conversion into a winter time snowblower. Very pleased with my results so far. Not bad for $100 for the whole machine and just about $30 for parts to get it running.