I copy and paste the https etc in the box at the very top of the screen.

I've not found a replacement 3rd party photo hosting site yet - hopefully Imgur and the UK regulator will get their sh*t sorted!

Ian, thanks for picking up the ball and running with it.

I gave the link and went through the annoying process of posting photos because you gave a lot of part numbers, but a lot of us have learned that some ebay sellers will assign an old sock a Yamaha air filter part number if they found it inside an airbox on a junker they dug out of a field.  

Far more common and even more tricky is part and bike miss identification by sellers.  

The ebay item you shared is definitely NOT the larger M or MX airbox.  Looks pretty rusty though.  

I'm not enough of an expert to positively say that one is correct for your bike, but it looks very much like it is.  I'm 90% sure but there could be some little detail for your year/model that I'm not aware of...  like I remember some of the earlier models may have had louvers on the side?  If you're looking for "concours original", those details might be important to you. 

 

The early DT1 airboxes has side louvres , but they were gone on the 71 model .
My parts book shows both 70 & 71 RT1 boxes not having side louvres .
The airbox on Ebay looks the same as the 71 DT1 , which takes the same air filter as an RT1 ,
but has a different prefix on the part number . Obviously there must be a difference between 250 and 360 boxes ,
perhaps size of air intakes ?
The Ebay box should work for you , but as Mark has pointed out , it's in a pretty sad state .

Thanks guys.  I may still go ahead as I have nothing at the minute and I am sure I can make it work.  

I will think over night.  

cheers to all 

Still on this subject I am afraid…. I don’t really want to make a concours bike, but would like to use period correct parts if I can as long as they are serviceable. I think that whilst the air box in question is rough I don’t think it’s going to be a pile of rust if I clean it up and paint it.. but….

As it is really a DT air box would the hose outlet be the right size for the 360 hose? Is the DT air hose the same as the RT1 hose? I don’t want to get the box only to find I can’t get the hose to connect to the carb.

Forgive me if I asking too much detail. I just want to have as much info to hand as I can and I don’t seem to be able to find the information anywhere else on line.

Thanks again..

We don't really know if it is a DT1 box or an RT1 box , but as it was advertised for a 360 ,
I'd suspect , that was the more likely source .
We don't know exactly what the difference between them might be .
The flange size for the rubber connecting joint might be larger on the 360 .
KDI probably have produced a replica rubber connector , and they might be able to confirm this .
There could be other members with RT1 and / or DT1 airboxes loose that might be able to compare or 
supply measurements for one or the other .
The Ebay airbox isn't a completely lost cause , but will require quite a bit of work to be serviceable .
Another option would be to try The Bike Boneyard . They may have one on a RT1 , so the source bike 
is not in question .
Whichever way you go , you'll likely have to replace the filter element , and the rubber connector .

My best guess between the air box part numbers is that the RT1 came without louvers in the side of the airbox in 1970. 

DT1 had the louvers until 1971 with the DT1E.   The 1971 DT1E shares the same airbox (without louvers) as the 70-71 RT1.

So the rusty ebay box would be correct for a 70-71 RT1 or a 1971 DT1 as far as I can tell.  There would not be any difference in the hose size on the box if my research is correct.