Countax K18-50 Ride On Mower And Grass Collector

Has done 855 hours and cuts and collects grass just fine stilll Powered collector and emptying both fine as the collector is only 3-4 month old. The mower itself hunts for revs when off load recently. When on load it holds constant revs fine. We put a complete new carb on it and that didn t fix it. So, reluctantly we bought a replacement and this one is in the way now. Collection only from NN7 1DL ....a car trainer should do I think