JD 690B excavator help...please!

If the batteries had life, disconnect them and charge them separately at 12V. If it IS 24V, the neg will be hooked to the POS of the other batt.

Now, no need to spin the crap out of the starter, find a friend, soak a rag in gas, and have him hold it inside of the air intake, (Air cleaner off) and crank it. It will run for a while on the fumes, OR, same deal, use an unlit weed burner.