It has window holes

DT2MX piston, slipper type. I see a two ring set in top pic. I'm not sure they ran a keystone ring on those. 'Tapered top surface of the ring'. Would have a K on top of the piston if it's keystone. Hope one of the rings in you new set is right for the job. I'm sort of familiar with those pistons--but was 50 years ago lol when my race bike was new & changed the piston & ring after so many races.

Thanks I will need to do some more research to see if I can use one ring out of the new set or need to order different one

scaring me... I'm just starting this journey.. eh.. 
How do you figure out if yer lean or rich? Sumthin' you do by ear perhaps?
Sneezles61

Well something melted the  piston after doing some research it shows that the timing is probably off the plug was to hot the needle jet valve in the wrong position carburetor needs cleaning and I need to check the intake for leaks
i am hoping the crank seals are good but all the other things I mentioned I will be checking 

The needle jet will not cause a lean condition because it's mostly open I think at 1/4 throttle so don't worry about that. Pinging is a violent explosion that happens to soon and it basicaly hammers a hole in the piston. Running lean I think will get the whole piston hot and would cause a seizure and cylinder wall scoring also. I had a dt at one time and I had to put little wires through all the carburetor passages to clear it up, it was a head scratcher. A lean engine will not run real well at lower rpms (poping ,backfiring ,idling to high if you know the signs and a rich engine will not run at wide open properly, blubbering, bogging fouling plugs.

Look in the Mikuni manual for the carb circuit overlap.   The slide needle and needle jet are the metering parts that have the most effect at 1/4 throttle if I remember correctly... 

Could be air leak.  Intake manifold leak is not as common on early reed models...  crank seals, base gasket, and head gasket are.

You don't need to remove flywheel to check timing... (and technically can't check timing with flywheel off)  but while in there look for oily residue as that's almost certainly signs of the seal leaking.

Make sure you have an accurate way to determine the exact moment the points open.  "Eyeballing" always results in advanced timing.

 

Thanks for the info I will look for oil residue hopefully I won’t find any I purchased a digital dial gauge that has millimeters on it i will be use that and a multi meter to check timing 

Meter must have an Rx1 scale.  I like analog meters...  most cheap and/or "autoranging" digital meters don't work well if at all.  They jump all over the place.

Yes I will be using an analog meter once all my parts arrive