I'm looking for some advice on where to start looking. I have a new to me with 1400 hrs ,Tak tl-6r with the Kubota v-2403 engine. As soon as I got it home I changed all fluids and filters. It has a surging problem at 3/4 throttle, smooth at idle to 2000, 2000-2300 surges, wide open 2300-2500 smooths out again. I hate to think that injectors would crap out at 1400 hrs, Maybe the computer sending the wrong signal to the injectors at that rpm? No codes showing. I turned the power management system off and it made no difference. I need a place to start please.
Pinch off supply line, loosen separator bowl under battery, mark and remove both fuel lines. Remove head assembly and clean out the inlet passage (elbow). I have lots of threads where that inlet elbow plugs with debris from the tank. My solution is to clean it out and add a "3972" inline screen. Search "3972" on the whole site here for more pictures and threads. It is not a Takeuchi/ Kubota only issue. My Cats have had it too.
To help someone in the future possibly the problem was a speed control resistor , the control knob for the rpm.
Thanks for posting what fixed it. May help more people than you think. Simon C