I'm down to the finishing touches on reviving a DT250A. How are the vent hoses routed and where do they terminate? Two crankcase hoses (cover and case itself), carburetor (2?), oil tank, and battery vent hoses need to be addressed.

The 1974 DT250/DT360 Factory Service Manual (available in Tech Library here) has fairly comprehensive routing diagrams near the back.

The 1975 manual has a little more detail and is worth a look if I remember correctly.  

Note: The bike should have had a decal under the seat showing the (critical) correct routing of the battery vent hose.  Reproductions are available pretty cheap last time I looked or you can find photos of the decal online fairly easily.  (Hint: searching the Internet for the part number of the decal usually finds one pretty quick. 438-28179-00)

Sometimes looking thru the owners manual and service manual you will see pictures of the carb area and vent tubes. I see a good picture of the carburetor in the owners manual on that bike that shows your carb vent tubes and both case vents.

I have a friend that has a DT250A with just over 100 original miles on it. Still brand new but he's to far away for me to go look at it to check the hoses. I've been trying to buy it now for 5 years. Maybe someday!