It is probably a GCV530? You can use the Sears parts system to look up. There is a diode box on these that I suppose could be funky like the one does on some Briggs twins at times. I only see a few a year but I don't know the price of a coil. Yes, twin coils. Do the spark plugs tell a story? Have 2 spark testers? These typically sit w/ 2 barrel carbs- maybe one tube has a blockage.

If it is a vee shaped twin cylinder, it will have a magneto/coil for each cylinder. Not much way to fire a vee engine off a single coil unless there is also a distributor in the arrangement.
Opposed twins operate just fine with a singe mag/coil design because one cylinder is at the end of the compression stroke while the opposite cylinder is at the end of the exhaust stroke when the spark occurs (wasted spark ignition style).

Yes, mownie, it is a vee type engine. So, on monday, i will pull the engine shroud to inspect it further, to make sure there are no bare wires that i can't see, now. I suppose those coils are expensive, aren't they? The engine runs ok-no noises, but misses. Not a steady miss, just sort of a stutter.
I had another tractor here that had one coil unbolted from its mounting area. The tractor engine would start and run well, but if i shut it off for a half an hour, it would not start, until maybe an hour, or a day later. I had installed new bolts to hold that coil in place, but it didn't help.
This engine is a Honda 16.5, V-twin, OHD cam, Pressure lubrication.
Model:917.273502 Serial no. 100903C001117.
There are new spark plugs in the engine, so they weren't the problem. This problem is an intermittent miss when running. The tractor can be run and driven, and will mow well--its just the "miss" that has me stumped.
I haven't done a compression test on it yet. Mainly because my tester is broken. And, at this stage of life, i don't want to invest in one! (89 yoa) Guess i'll go see Old Uncle Joe, and borrow his tester. Thanks! RJ

Reading the color of the spark plugs will give some clues about what an engine is doing.
If this engine begins misfiring or "loses a cylinder" when the engine is hot, it could be from loss of spark...........or it could be from insufficient fuel to the affected cylinder (as mentioned by tomplum).
Reading the spark plugs after running the engine for 10 or 15 minutes AFTER it begins misfiring, and then shutting off the engine and "reading" the plug color may help discern whether the miss is fuel or spark related.
If the miss is fuel related (lack of fuel), the plug electrodes and porcelain insulator will be a bright white/silvery color and may even show signs of "blistering" (on the affected cylinder).
If the miss is due to spark loss, the surfaces of the plug will range from dark brown to black (on the affected cylinder)

Mownie: I removed the spark plugs, and found the right side plug was very black, so i installed another one, and mowed the whole back yard-never missed at all.
But, next day, the miss was back. Heck, i'll run out of spark plugs if i don't get it fixed!
I haven't opened up the flywheel cover yet. I'll do that maybe today. And, the tractor that was in the crick runs well, and son took it to show to a friend, for possible sale.
Rusty Jim

Would that be "shiny, oily looking black" or "dry, powdery looking black"?

Mownie: It is dry, powdery looking black. If it means a lot of work, getting into the innards, I'll sell it as-is. Lots of good parts in it. Unless something shows up soon, it'll get the heave-ho! It still runs, and mows, but---well---I am not going to put a pile of money into it.
I just sold the "Creek tractor"! Son brought the cash at lunch time. I polished it all, and checked everything, but i couldn't find anything wrong with it.
Thanks for the free advice! Rusty J.

Rusty, a dry, powdery looking black soot on plugs means the cylinder is too rich in fuel.
This engine likely has carburetor problems.

Thanks, Mownie! I'll do some further inspecting of things. With Ruth being sick, and hardly able to do anything, i don't have much time to get down to garage, but i manage to find some time to get things done!
Rusty