Hello, I am looking to acquire a 12F grader (serial 73G619) and one stipulation of the sale was I wanted it to start or at least turn over. I finally got a set of 4 new 6V batteries in it yesterday and it appears it's locked up at first thought. Reason for the question is I am at 26V before I turn the start lever then I drop to 10-12V. I know that is never going to turn the engine over. I also put my charged 12V 4000amp jump pack across two batteries and it doesn't help at all. It's display goes from about 13V to 5V. I can hear and feel the starter Bendix extending to the flywheel so I feel it is ok. I am pretty mechanically inclined but not with this grader. It is a clean grader with no hacked wiring or butchery of any kind. Which is why I really want it. I am assuming the starter solenoid under the dash that has the switches is weak? I did subscribe to this site so I can have access to the documents library but I just did that this morning. Judging on the old batteries it has probably sat for 15-20 years and of course it's outside. I appreciate the help.

Seems you have a major short/ground in the stater circuit.

First make sure the engine will turn over as in not froze up.
Then check the disconnect night switch.
Get a 24 volt head light and wire it up with two test leads, hook one wire up to each post on the starter solenoid so the light comes on.
Now take a volt meter and check each connection from the battery post to the solenoid both sides for voltage drop.
.If you find no bad connections you will need to pull the starter.
Good luck
Bob

Check that the motor turns freely. If you remove the starter motor you can hook all the leads up when it is out on the ground and operate it to see what it does. This is a quick bench test to see what is happening. The bendix should throw out and spin really quickly and freely. I have held bits of wood against the bendix to provide load to diagnose starter problems as well. Good luck.