I have no problems with engine at all. IT's a little loud, but it runs well and there is plenty of power. My problem is that it has about 134 hours on it and seems to spend more time in the shop then anywhere else. Mostly for transmission and related problems. My main complaint is that it leaked and for a machine of this calibur, the transmission is very weak. Kubota had some known issues with the first generation trannys in these things....primarly the fact that they used bushings instead of bearings for the rear axles. That has since been corrected and the newer ones have bearings. The bushings isses caused a lot of leaking after they got a few hours on them. Mine was upgraded after I had it in about 5 times and when I got it back, it was still leaking. It went back and has not leaked since, but I hve only put a few hours on it since...the machine only has 137 hours on it total. They have already had to replace the glide steer cables as well, but they have redisgned the mounts for the new ones so in theory they wont break again..... at 120 hours. My main complaint now is the the the trasnission is incabiable of delivering the power to the ground. It , in my opinion is very weak. I do not advocate spinning he tires over on a tractor just for grins and giggles, but if it gets into a bind....(pulling a cart, pushing snow...whatever) it should have the cabibility of spinning the tires. Otherwiser how does one know if the all of the aviable power is being delivered to the ground? Mine just sits there and whines. For a machine that cost 8K, I expect more then that. As far as fuel ecomany goes, I have and 18hp gas gravely that uses three tiems the fuel of this Kobota given the same work load......but, it also handles said workload nuch better.
If all you're after is cutting grass economicly and reasonably quickly, with all the improvments that have been made, the Kubota might be a good choice, but if you're wanting anything else and mine is representative, I would go with something else. The last time mine came back from the shop it was in there for the sole purpose of the Kubota rep to go over it and and make any necessary adjustments. When it came back to me his words were, "it pulls as well as any GR out there". I haven't really had a a chance to find out yet, but I guess we'll see.
There are others on here that are totally satisfied with their GR's. There is one guy who has made many very nice attachments for his and he loves it...maybe he'll put in his two cents worth. Maybe i got a bad one, but I am a long way from being satisfied. Good luck with your decision.
Chris