13 xp900 swapped to 1000 motor and now it constantly overheats

My buddy swapped his 900 over to a 1000 motor and now we can’t get it to run cool. It just steadily climbs 220-230 and then we shut it down before any damage was done. We bought an upgraded 1000 radiator and installed it but still no change. Any help here? We have to be missing something obvious !

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