Hey guys hoping for some help.
I am new to the dt world and have recently bought myself a 1972 dt250. The wiring has been mucked with and i am having trouble finding a wiring diagram for this year.
what i currently have wired from the magneto is.
Black - coil
White - rectifier
Yellow headlight
Green - indicator switch
can someone help.

How are you determing the age of your bike - registration document or date of manufacture stamped on the frame?

You almost certainly have a 1972 DT2 (yellow/orange paintwork) or a 1973 DT3 (dark green paintwork). They are mostly identical bikes. The DT250 wasn't introduced until 1974 and is a totally different machine.

If you compare your frame and engine number(s) to those in the VIN table in the Tech Library (see top toolbar above), then you will know exactly what you have.

There is a wiring diagram at the back of the Service Manual held in the Tech Library, although I have tried to attach a link below.

My 1972 RT2 (360cc version of your bike) has six wires coming from the generator - black, green, green/red and yellow and these four connect with the main harness roughly underneath the back of the petrol tank. There is also a white wire in the same batch, but this is basically a spare and is not used. Finally, there is another black that exits the harness from the generator about half way up (roughly at carb height) and this is used for diagnostic purposes only - it shouldn't be connected to the main harness.

If you could post a photo of what you have by way of coils and wiring in the flywheel area (under the left crank case cover), then that will enable the real experts here (which I am not!) to say what is incorrect and what is missing.

Vintage Yamaha Enduro Fans - 71-73 DT & RT (250cc-360cc) Service Manual (yamaha-enduros.com)

Thanks mate i viewed the manual and that helps.
reckon i need to rewire the main switch.
I did a vin check and it is a pearl yellow 72 dt2 250.
I believe the green is a day time charge cable. So i will disconnect that from the indicator switch and wire it correctly. 
Also would you guys recommend installing a regulator into the yellow head light cable.

 

Yes to the 6v regulator, but it wires into the blue in the headlight bowl - see the appropriate Service Bulletin in the Tech Library.

You may not be worried, but that doesn't look like the original mounting bracket for the clocks. If you want to go back to original, I may have a spare, albeit with the smallest of kinks in it (I'm near Salisbury, UK).

If the indicators are missing and you want to fit some, post here before paying silly money for them + fittings!