I have what I think is a 1972 RT2 MX 360. The silver paint with the black and red stripes on the fuel tank sure looks like a 1972 from the images I have found on the web. The VIN numbers on the engine and frame are matching numbers. Both VIN numbers start with a RT1 and fall between 185101-191618 which according to the VIN search say this is a 1972 RT2 MX 360. When the VIN begins with an Rt1 it makes me think this is a 1971. The question I have is what year do I look under when searching parts for this motorcycle. A 1971 or 1972 model year? I have been looking for a brake torsion spring for this motorcycle and have found the spring is different between 1971 and 1972. The spring on my motorcycle does not look exactly like either spring. Any ideas? Thank you in advance for your help.

Vin numbers for RT1/2/3 are all prefixed with RT1, so you have a 1972. 

It looks like it may be a "one year" part?  I could not find pictures of the 90508-29048-00 anyplace.   Appears to have been superseded by 322-27216-01 which I couldn't find a pic of either. 

This part?

YAMAHA DT2MX RT2MX C.1972 GENUINE NOS REAR BRAKE PIVOT SPRING - # 90508-29048 | eBay

Will have been 322...........first, superseding to the above.

If you need it and he doesn't post overseas, bung me the dosh and I'll buy it for you and post. I'm in the UK and have done this for other US members here, so I won't scarper with the dough or part!

It looks like it might be very similiar to the standard RT2 item based on the pictures on partzilla (which is always a little dicey).

I happen to have a DT2MX frame in my garage sitting next to an RT3 (which is same as an RT2).

I unfortunately do not have the brake pedal assembly or any of it's associated parts, but I can probably take a look and get an idea if the RT3 spring would work. I'm thinking it probably would based on the partzilla pictures.

I saw this exact picture of this torsion spring on ebay. My spring looks a lot like this spring except the left end of the the spring in the picture has a U shaped end. I wasn't sure if it would work. Thanks.

Thank you!

Not sure if this is any help at this point, but here are pics of an rt3 spring.

I'd be interested in seeing the dt2mx setup to see if the rt3 spring will work, as I'll be trying to figure this same thing out myself at some point.

photos.app.goo.gl/Eift9VMHSf8TbkRP6