HELP please! Kubota v1505 in kx71-3

[Tom7810]

Hi I have a Kubota kx71-3 that was over heating as the head was cracked. Got hold of a full running second hand engine and swapped it over, starts runs and revs up. As soon as you use a hydraulic functions rpm drops, dead end the function and engine stalls out. Even with it running flat out it will stall.
have checked low pressure fuel supply 12v pump and replaced filter. Swaped the high pressure fuel pump and injectors out of the original engine that ran fine just overheating. No different. Noticed it was sounding rough and blowing by on the valves. Adjusted the clearances, no better. Took the head off to find one valve had hammered the seat. Had the head fully referbished with a new seat put in and all new valves, ground and lapped. New seals and the head skimmed. Have refitted to the engine and set and adjusted the clearances all perfect.
had it running and still exactly the same issue of it stalling.
any ideas where to go next? Could it be the governor? What can I adjust?
Believe I have the fuel pump rack in the right slot. Don’t think it would work in the wide slot?
I’m pulling my hair out!
any help is much appreciated.
Thankyou

 

[North Idaho Wolfman]

What is the compression numbers on the cylinders?
What is the exact model and serial number of the replacement engine?

 

[Dustyx2]

Did you disturb any of the hydraulics when doing the swap? Are you sure the hydraulics aren't deadheading stalling the engine? Maybe a solenoid valve or something left disconnected? Hoses reversed maybe? I would assume there would be test ports for a pressure gage that might be helpful.