Hi guys 
Iv recently purchased a dt125mx which its had to have a crank rebuild . 
the bike has a points system and I’m totally lost on how to do the timing now iv rebuilt the bike . The stator plate thing is fixed on with two screws and there’s no adjustment on the plate . I have a manual but it covers many models and I’m not to good with electrics on bikes , any help would be great as I’m now pretty stuck . Thanks guys 

Your options are limited to points gap for timing. If ya into dial gauges then set the piston at 1.8btdc & have points leaving each other at that 'point'. If you have an ohm meter set it on lowest & connect to the points wire black in the stator loom up away from the motor & with kill switch open the meter reading should vary [very slightly] at the moment of cracking to open.
My explanation might be confusing so wait & "see what others suggest".
I'm thinking you have a center plug head on yours so easy to dial gauge.
I shouldn't tell you how i'd do it--ok--just set the points max gap to 14 & carry on.
but ignore that & i'll get scalded now haha.
Think they're a fairly mildly tuned little motor & not fussy like a racehorse.
Be sure the flywheel nut is super tight too.

Yep. From what I remember from ty80s, 125s and 175s, my techies when swapping points, just set the gap at 14 thou and double checked with the pocket tester.

Cannot remember if there was a timing mark on the stator and rotor or if the lads just made one, but 14 thou and checked that the points were starting to open on the mark. Was it a black and white wire you connected to? Twenty years ago now so cannot remember the finer details.

thanks guys , very helpfull , cheers