If your certain your batteries are good/hot, the simplest thing to do is use a test light looking for bad cable connections working your way from the batteries to the starter. It's very simple. I assume you have a 24V system with two batteries in series, and hopefully, your two batteries are next to each other.
Start at the batteries. Place the probe tip of the test light on the master positive battery post, not the cable terminal. Place the ground clamp of the test lamp on the master negative battery post. You should have a bright lamp. Have someone hit starter switch. If the light remains bright, batteries good. Move the probe to the master positive battery cable terminal. Hit start again, bright light...good connection. Move tester ground clamp to negative cable terminal, test again, bright light, good. Move the ground clamp to a good frame ground on the machine, test, bright light, good. If the lamp remains bright during these tests, you've established your batteries and connections are good. If the lamp goes dim during any of the tests, you've located a bad connection to repair.
Follow positive cable to the next termination, which will probably be the battery post on the starter. Connect test lamp to frame ground, probe on the battery post on starter, lamp should be bright. Hit start, if lamp remains bright, move probe to starter motor output of solenoid. If it's dim or no glow at all, check the switched wire at starter solenoid at this time. If the lamp glows dim, you probably have a bad connection in the switched wire circuit. Check the same way with test light. You might have to start at keyswitch looking for a drop in voltage causing a dim lamp. If the lamp stays bright at the starter switched wire when operating key switch to start, but doesn't have a bright lamp at solenoid output to starter, you have a bad solenoid. I hope this helps you a little.
