You are air locked. Dont run it that way. The new models have several air bleeds because of this. Probably should drain and add back very slowly until you get the same amount back in.
Also keep a close eye on the engine cooling system. Never let it overheat or the head cracks. Usually just keep the crap blown out of the radiator and frequently check the expansion tank. Run it hard they like to run at 3800 rpm all the time for many many thousands of hours .
On the rtv for long service life always use kubota sudtII AND none other brand. Use oem filters. Change the hst oil at least every second year unless you reach the service intervals in hours first. Don't wait for the hours. And if you must clean the engine transmission don't use water. Use...
Please remind me what the manual says about the relief valve and spring? Does the manual give a length spec for the spring? The redundant question.. has the oil been changed and replaced with sudt and are the filters oem and in the correct position.
Look at the shifter assembly on the trans. One lever moves the shifter left and right the other forward or backwards. Notice when you use the shift lever on the dash that the lever will move the cables differently. Put the transmission and confirm neutral then confirm the shift lever is in a...
You have a kubota rtv 900 model that is made before the X 900. Your mate probably has the shift forks out of alignment. Remove the bolts from around the shift assembly in your pictures and remove straight up. With a long screw driver slide the gears into neutral and then match the shift forks...
Now that you have photos? Use them as a time stamp. Run the engine but don't drive it and see wich one of the numbers advances by tenths and wich one stays unchanged. The one that changes will be hours
Your pressure sounds ok. There are limits to how high you can go before cracking the case though. Have you done the peddle and hst speed lever adjustment? Did your engine hold 3800 at stall?