I have a remote crank button that I have used for a long time. One clip goes to the starter, one clip goes the positive battery terminal. Push the buttone and the engine cranks. If you want the engine to start you have to turn the key on to energize the ignition system.
2 nasty pictures of my starter before I rebuilt my engine. One shows where the clip goes after sliding off the connector from your ignition switch, I put an arrow on the pic. The other photo shows it actually hooked up with the wiring all there.
Making a pushbutton and clips can be of what you have on hand. I am fortunate to have tools on hand. I started rebuilding and working on engines in the 1960's. It was my entire career.
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