I have a kubota bx25 that won't start. it has power to the starter on battery side

check grounds first & then have starter & battery tested

jump starter with battery if starts look for bad ignition switch or battery dosnt have enough amps or bad contact in silinoid you have to buy one to find out

is parking brake on? rememeber pedal might show it's off but brake switch thinks it's not

Sounds as though the battery is no good,
unless you know otherwise & also had it tested
Charging a battery doesn't address it's internal
condition
You have battery cables that corrode inside & can be
voltage drop tested
You have the starter & solenoid,ignition sw & such, to name
a few,lots of possible causes & things to check

CHECK BATTERY GROUND AND CABLE TO STARTER ALSO CHECK STARTER WATER IS BAD ON STARTERS AND GET WET AND SHORT OUT MEASY GOOD LUCK

check battery check to make syre you are getting power to small starter wire when key is turned

How about corroded battery cables (internal)

Fusible Link wiring corroded & open circuit,does
everything electrical work except the starting circuit?

Turn key & have power to starter solenoid ?
Neutral Switch !
Ignition Switch !

Tough to guess without wiring diagrams,
to see where to start testing

Can't fix what you don't know you have

Check batry terminals are secure & free from corosion, check security of earth strap to engine & main power wire on starter, if ok have the batry load tested to ensure it can perform under load as the starter needs a lot of current. Have you tried a jump start?

you could just have dead cell in the battery which isn't getting enough amps to the starter,, have the battery LOAD checked,, that will tell you if the battery is actually good, just because it registers 12 volts isn't necessarily an indication that the required amps are present.

Now you have a good battery & a starter that turns over the motor

Have you cycled the key on & off with a fuel pressure gauge on the
fuel rail?

Do you have a fuel filter that isn't over 3 or 4 years old?

Have you checked for spark while cranking ? Use an old plug on the wires,
if you have ignition wires,don't ground the wire without resistance

If you removed the ducting & MAF Sensor it won't start

Tell us what you checked & exactly how that was done.