Rt325 
 here is a decent picture of the clip that was in my hub and here is a picture of 2 new NOS circlips off eBay 

I was gonna wait about ordering them till I made sure the one I’ve got is incorrect 

I also included a picture of the thickness of the clip it’s 2mm and I checked it in the groove and it was basically the correct width for the factory groove

here is link to pictures and thanks again for your help!!

imgur.com/gallery/yamaha-rear-wheel-cush-hub-circlip-SLykX5y

Well that's me standing in the bad boy corner. Living and learning lol. I'll go look at my dt1 later. I did just look at a genuine 175 circlip on fleabay but the link won't take on here. 175 hub is smaller of course but same principle. That circlip shows what I expected for a 400 with ears sticking up so circlip is touching bottom of the groove full circle. Cheers.

I'm not meaning to keep this post rolling but this is the type i meant cheers. Well actualy i was thinking ears sticking up but anyway--fits mostly full circle in the groove. www.partzilla.com/product/yamaha/93440-2...0&submodel_name=null

Well this is interesting I’ll research more the partzilla link says the round clip also fits the 1976 DT400 which is the same as the 1975. Good info and I really appreciate the help and I enjoy learning more about the bikes I work on. 

I’ve got a 1974 dt250 right here beside this 400 I’ll look and see what is going on it.