Your engine was made on 24 June, 1992. I don't think SB45s were being made by then so I think it may be a replacement, but what we need are pictures of your mower, so we can see how the engine and mower match each other.
Here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6ntACVJ1DajI.pdfHere is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/flivAJX-nfBhU7y.pdfThe most important piece of information right now, is that it was made later than 1982 so it has Magnetron electronic ignition, not breaker points. This simplifies finding out why it has no spark. In most cases where a Magnetron ignition system stops working, the problem is not in the module, but in the kill wire circuit. This is the system for shutting down the engine. There will be a thin black wire coming out of the Magnetron module, and running to the governor plate near the carburetor. We need to disconnect this wire at the module, then repeat the spark test. If there is no spark when the kill wire is completely disconnected, right at its source (the module), there are only two remaining alternatives: defective grounding of the module, or a failed Magnetron module. So, to disconnect the kill wire from the module you need to remove the cooling air cowl, complete with pull-start. You will then see the module close to the outside of the flywheel, with the high tension lead from the spark plug running directly to it. Find the thin black kill wire running to it, and disconnect the slide-on connector at the module. Now remember: with the kill wire disconnected, you have no normal safe way to stop the engine, so you can only test for spark by looking at the gap on the spark plug as previously. You can rotate the flywheel with an electric drill, or temporarily reinstall the cowl and starter. Please report whether there is spark when you make this test.
