What carb exactly is it, will be marked on the base of the carb edge, there are two fitted to the xr2, the later ones were a bit smaller and weedier power wise, but better for emissions, these had a vacuum secondary, they always jam, the secondary usually due to lack of use, that puts it down to around 55bhp!!.
The earlier carb is the best, as fitted on the xr3, better power and pretty much as good on mpg front when set right.
The later carb is a synchronous carb, where the 2nd venturi will open when the primary is around 2/3 open.
The early, 81-86 carb is a 32DFT, a slightly smaller venturi version was even used on the 1300 XR2, but your version as all 1.6 had venturis of 24 and 25 mm, the later carb 86-89 is a 28/32 TLDM, with venturis of 21 and 23mm, and again vac secondary.
There is something drastically wrong with adjustment if you cant get on the early carb both venturis fully open at full throttle, and certainly the primary venturi on the later carb, the one with choke flap on top of it is the primary.
I would check you are getting full throttle movement first.
tabetha