Engine runs fine with no load but once in gear it bogs down and is very slow to start moving on flat or descending land. And has even less power when I try and climb any up slope.
Fuel pump is fine. Pressure is 43 psi.
Voltage is over 13 vdc.
Temperature self regulates.
With rear end off ground wheel seem to turn fairly easily.
Symptoms show up as soon as I try and go forward or backwards.
With the CVT cover removed , and just sitting, I have watched the pulleys expand and contract easily as I rev up the motor. Belt is original but measures well over minimum width.
2011 but new to me. Just sat on dealers lot and used for parts until I bought it a year or so ago. NEVER been driven in the hills just running around a 4 acre lot to get from point a to b.
I am old and stumped.

[2015 Z Force 800 53/Trail EPS]

2011 was the very first year of the Z Force/Snyper and it was only the gen-1 600.  I would test the compression and if low, do a leak-down to see where it's going. If in spec, and I do hope you have a service manual, check the valve timing as they were known to jump time..because many came with miss-matched cam chain and sprockets. If you need a service manual let me know..I do have one.