I'm new to the group and wanted to see if I could pick the brains of some of ya'll. I inherited a 1970 DT250 Enduro from my grandpa after he passed and I've been slowly replacing parts that need replacing or for parts that are missing and as to be expected most if not all of those parts are extremely hard to find or I'll find a part that is similar to what I need but not compatible with my bike and year. My main question here is if there are later models of the bike that have parts that are still compatible even when it's stated that its not? I'm new to the motorcycle scene and especially vintage bike scene so I apologize in advance if my questions are stupid ones. Any help is appreciated. 

 from near Salisbury, UK.

No such thing as a stupid question!

Some parts are still available from Yamaha. Check on Partzilla (US) and CMSNL (Europe) amongst others. I think that Speed and Sport and HVC might be worth looking at as well.

If you select a part on CMSNL and Partzilla, they will often show which other models used that part.

KDI (see banner on the right of the screen) and Clauss Studios sell repro parts.

Please always feel free to ask specific questions here. 

Thank you for the response! I do have another question maybe you can answer or point me in the right
I'm missing the rectifier for the battery and as I'm searching online I can't seem to find one that's compatible. Could I just use any 6v rectifier?

Rectifier is just a heavy duty diode.  

Yamaha still supplies a replacement, looks different than the old "plate" rectifiers the earlier models had but will function perfectly.

White wire goes to terminal marked "~" and red wire goes to terminal marked "+" on the new rectifier.

www.partzilla.com/product/yamaha/353-819...d8d32af457baecbea400

Funny story about those plate rectifiers like honda CT90 had & i think the light switch on the bars bought in the extra coils when lights on. Had one 50 years ago--glosh-- that Mr Farmer bought in not charging. Alternator was earthed out internaly so in desperation as a trial & error i un-earthed the multiplate rectifier==green alway earth on Honda, sorry honda not in capitals--& bugger me it charged plenty so Mr Farmer carried on. Not sure for how long but anyway!!. I remember wrapping the rectifier in an inner tube so it couldn't touch earth--just in case--but don't recal him coming back complaining of burning rubber haha. Main reason i did that was parts down here in NZ are--were--& are, just crazy expensive. Anyway, i'm sure you wanted to know that!!--Not. Obviously that can't work with Yamaha system as Honda was a true alternator not earthed--except this was was shorted internaly to earth.