I'm throwing that out, but since you've replaced a battery... Is the Left hand side battery connected the right way ? I'm talking about the battery that's used for the 24v cranking. It has to be mirror from the right side battery. Not the same part number because + and - are swapped.
Also, try disconnecting both batteries and measure the voltage on each one individually.
Also, when i bought my hdj81, i've spent quite sometime trying to understand the 24timer and cranking relay...
Basically, the timer is there in order to delay the cranking relay slightly.
First, it instantly turns on the big voltage converter relay, then after some little unoticeable delay, it turns on the cranking relay and also the starter solenoid. This prevents wear from electrical arcing inside the voltage converter relay. The starter is then the only one doing the heavy lifting. It could be something with the voltage converter relay. This one sits on the left hand side, under the dash, by the fender. Its up in there. It looks like an old school tin-can relay. Maybe you should the that one out and see if the plug looks allright.
Also, try disconnecting both batteries and measure the voltage on each one individually.
Also, when i bought my hdj81, i've spent quite sometime trying to understand the 24timer and cranking relay...
Basically, the timer is there in order to delay the cranking relay slightly.
First, it instantly turns on the big voltage converter relay, then after some little unoticeable delay, it turns on the cranking relay and also the starter solenoid. This prevents wear from electrical arcing inside the voltage converter relay. The starter is then the only one doing the heavy lifting. It could be something with the voltage converter relay. This one sits on the left hand side, under the dash, by the fender. Its up in there. It looks like an old school tin-can relay. Maybe you should the that one out and see if the plug looks allright.