Kubota RTV520 - smoke and stall issue

[fikey]

I am about 6 months in to owning my 520. It is used mainly to run back and forth to our barn and shop. Occasionally, I run it up and down a few fairly steep hills on the property. One day, as I was going up one of the hills, the motor started sputtering and a tremendous amount of smoke was coming out of the exhaust. I was near the top and it made it (sputtering) up. Once back on the flat, I made it home. I loaded it on the trailer and took it back to the dealer. They said they checked everything out and found no issues. Over the next month or so, I only had occasion to go up hills once or twice with no issue. Then one day, again as I was going up a hill, the engine sputtered, giant plume of white smoke and then the engine died. 30 seconds later, started up and made it to the top. Repeated the route (down and up) and the same thing happened again. Called the dealer and their head of service said he would come out and wanted to see it first hand. He came out a few days later and repeated the route several time and it never happened with him in it. I had videoed the whole thing on one of the times it happened to me, but since it happens intermittently, could not produce it when he was here. I told him that I had checked the temperature, the oil level and the antifreeze level after each occurrence and they were normal. I asked him to call Kubota and ask what the possibilities were and that I am not fond of it dying on the hill and blowing the smoke and I didn't want to wait until something catastrophic happened to figure it out. When I followed up, they had no answers (which doesn't exactly please me). Any ideas? The attached photo was the start of the smoking. Didn't know how to upload the video of the whole thing, but it fogged the whole area.

[klm]

head-gasket maybe

[fikey]

Don't think so. The fact that the problem is intermittent (can repeat climbing the same hill over and over and it won't happen), no oil in antifreeze, no antifreeze in oil and no overheating. 

[klm]

water in the gas ??

[Joe Breaux]

Thats coolant ..