Hello, I just purchased a 71 RT1 360 close ratio model. Would like to know why Yamaha made this model. I don't see that they continued it in future models. Appreciate any information you can provide me. thanks

Hi, by no means an expert, but have not heard of such a model before. Are you in the U.S.? I would imagine that you can tell by shift points/RPM, but are there indications on the bike of it being close ratio?

VIN table confirms details of the close ratio gearbox model.

360 & 400 cc VIN Numbers

Short answer:  The optional "close ratio" transmission ratios came from the new off road only and modified for motocross at the factory "M" models.  

One of the features of Yamaha's "Enduro" line introduced in 1968 was that you could remove the street gear and competitively race it in motocross and scrambles events for example.  (The concept of the "Enduro" was pretty much detuned motocross bike that came with street legal lighting from day one)

You could actually ride to the track, remove a few "street" parts, race competitively, put "street" parts back on, and ride home.  Yamaha sold "GYT" parts to modify your Enduro engine for racing.  

The earlier 250 enduro models (68-69) had more or less a "close ratio" transmission... the ratio gaps were a compromise for street, trail, and racing.  

Motocross racing took off and very quickly it became more of a need to have a purpose-built motocross model if you wanted to be competitive at the track.  Yamaha introduced their "M" (for motocross) models in 1970, (along with the new 360 RT series Enduro and Motocross models)  

One thing that came from this evolution was to give the "M" models a better close ratio transmission for racing.  The Enduro versions also got a better new wider ratio transmission that had low gears for plonking on trails and the higher gears were taller better suited for highway use.  

Perhaps as a marketing move, for a couple of years Yamaha sold a special version of the Enduro that came with the new "M" close ratio transmission.  The dream of having one bike you could race motocross with competitively on Sunday and ride to work on Monday was not dead...  yet.  

In 1972, the 250 and 360 motocross models really started to stand on their own.  The days of being competitive in motocross without a specialized motocross model were almost dead.  If you wanted to race motocross, it was no longer smart to start with an enduro!  Yamaha completed the switch to selling a purpose-built competition model for motocross alongside the enduro line and stopped offering things like the "close ratio" motocross transmission option in the enduro.