Welcome to the forum! Do you have an Owners Manual for this? I has a wiring diagram in it. I'll attach a copy here just in case. No spark can be several things, bad coil, points or condenser. You can unhook the condenser to see if you get spark then, but leaving it off will burn the points quickly.
Do you own a Volt/Ohm meter? 1st Check and see if you have 12v going to the coil with the key in the Run position. If you do then either your Coil is bad or the Condenser is bad or both.
I've replaced quite a few Onan coils with 5ohm 1965-1984 Harley Davidson Points ignition coils. Used to be able to get them for $30 but the prices are up quite a bit on everything. The older Kohler K482 / K532 / K582 / K662 / KT17 and KT19 used the same type of coil and they rarely go bad.
These aftermarket Chinese Kohler coils will work but Don't ask me how long they will work.
You will have to put a longer wire from the points to the coil. (atleast I had to on my neighbors because the original wire was hacked up and to short) But other than that you will have a reliable coil that will last a long long time as long as you don't leave the Key in the run position with the engine not running and cook the coil. Any coil will quickly overheat and burn up if you do that for more than a couple minutes.
Amazon.com : Stens 055-137 Condenser, Black : Lawn And Garden Tool Replacement Parts : Patio, Lawn & Garden
Those Kohler Condensers will not fit under the points cover. The Onan condenser that fits under the points cover is around $65 which is absolutely ridiculously over priced.
If you need a new condenser just hook it up to the negative side of the coil and mount it under 1 of the coil mounting screws. You could go to any good Auto parts store and buy a Standard brand Automotive Condenser and use that. Any condenser will work when it comes to Points ignition parts.
Pic of his FF20 and where I mounted the Harley coil. It's been on there and working for about 6 years. Really wish he would keep it in his garage out of the weather but his wife insists on parking her car in the garage. 🤔 lol