Quick question,kick starting mt DT3 typically results in a kick back through the starter. I think the ignition is too far advanced. How do I retard the ignition?  I have a Dial Indicator. Thanks. 

This should help, along with your manual
DT250 timing
Here's another:
DT2 timing
 

You asked how to retard the timing and not check or set the timing to spec...

Quick and dirty method to retard timing is narrow the maximum point gap slightly.  Say if it's 0.015" now, set it to 0.014" or 0.013". 
 
But best method is to set timing to spec.  (Note that you set timing by adjusting point gap until points just open with piston at the correct distance BTDC.  If you try to do this "by eye" without an accurate way to determine the exact moment the points open, timing will be advanced.  Once timing is set to spec, you don't touch the point gap)

Be sure the flywheel key is in one piece or even if it's been moving it could step the key enough to over advance the timing before it finaly gives up & breaks off sending timing too far away to run.
Sorry--that sounds like scare tactics & it's possible the problem only points set too wide.
250's don't normaly kick back hard unless just playing softly when kicking through, or starting your kick from half way down.
Kick from the top against compression so you get a good kick right through & that way it will go through compression a second time before the lever hits the footrest.
Umm-That's in a perfect world.
3.2mm btdc on those but could retard it to 3mm safely i'd think.