The
L4400 has inadequate wiring that connects the battery to the starter motor. The battery terminals are thin and inadequate small terminals connect the 50 amp fuses.
After several years these sections with be clogged up with dust or even have some corrosion, you need to disassemble that area and file the metal connectors with round/flat files, sandpaper or a wire brush.
The area that the chassis is grounded to doesn't give a good indication that it connects to the rear of the chassis properly, mine was attached but separated by painted sections of metal plates. You may need to reground a better section of chassis.
You may even want to completely change the battery terminals with proper ones. Oli express and abay also have resettable 50 amp fuses, they are worth using instead, because if you blow a fuse, its likely the Kubota shop won't have a spare 50A fuse in stock anyway.
But for me even after cleaning this area, the 12 volts that connected to the key switch still had dropped down to 9 volts after, which indicated the key switch was corroded and was unable to pass a current properly.
You may be able to start the
L4400, but have the starter motor fail on you where it stops and starts making a clicking sound instead. This may fool you into thinking the battery needed replacing.
Or the
L4400 wont start at all, and the only way you can get the start motor running is by connecting a lead from the 12V positive battery to the terminal section of the starter motor. This is a dangerous thing to do if the tractor is in drive, but as long as you keep the footbrake on, the lever in neutral, you should use long lengths of jumper cable to distance yourself from the movement of the tractor also.
The starter motor has two electrical connections - one with a large ring connector that goes directly to the battery, unswitched, using a 120 - 170A cable. The other smaller connector is a spade terminal that goes to the ignition key switch via a thin cable in the loom.
From observation the spade terminal that activates the starter motor is using way more amps than it should. It shouldn't be using more than 8 amps. To fix things properly (to keep the safety mechanisms intact) you should order a new key switch mechanism and replace the oem relay that it connects to. If those 2 weren't the problem, rat chewed cables are common problems also.
I fixed mine by connecting the starter motor output to a 12v auto relay that is positioned near the battery and connects a 12v through a thicker wire to the spade terminal of the starter motor. The safety mechanisms still worked also.
There shouldn't be any significant corrosion between connectors, but if there is, its often from connecting dissimilar types of metal.
