I purchased this JD 850 tractor for some bush hogging and light discing. It has a 3 cyl Yanmar diesel and runs fine, however when I go to engage the PTO, there is a grinding of gears. The only way I hav been able to work around this is to completely shut down the tractor and re-start. Just as the engine fires and RPM's are lower i engage the PTO and press the accelerator to get the bush hog going. THis cannot be right. Any answers as to what I need to do? Thanks