A few things... USA used the "B" and "C" for 1975 and 1976. Other countries likely didn't. And other countries are going to be similar to but not exactly the same as the US models in terms of wiring and mufflers to name a couple things.

Unfortunately, almost all literature and parts lists online are for US models.

You need the whole number to tell the year. There is some UK VIN info in the Tech Library here.

Here's a link. DT400 is at the bottom.

yamaha-enduros.com/index.php/uk-vin-information

VIN Number confirmed as 513-100404

Should be a 1976 then.

I have a Haynes manual for the DT RT series as well as the 1974 DT360 and the 74-76 DT250 and 1975-76 DT400. In that manual which was written and published in England, They did a tear down and overhaul of a 1975 DT250 B. they referred to the 1974-76 models as A B or C depending on the year. At least in the UK they referred to that as such.

So is mine a 'C' then?

There are some Service Manuals for sale on fleabay.co.uk. One of these is well worth buying anyway, but they often show the VIN numbers vs models at the front.

Haynes wrote US-based manuals as well as UK-based manuals. Sometimes the US market Haynes manual contained UK model photos but for the most part they were tailored to the vehicle as delivered in the US market. I used to have UK and US Haynes manuals for some of the cars I had decades ago... it was interesting to compare the differences (beyond steering wheel on the wrong side!)

I'm curious if your Haynes lists the UK 513 serial number prefix and the different UK wiring diagrams?

I don't recall it having vin number prefixes but the featured DT250B was competition yellow like our DT400 in the US. the spelling is different, Gasoline is called Petrol and Tire was spelled Tyre and many other examples not coming to mind right now. I need to dig that manual out and scan it or something.

Idle is referred to as Tick Over in that book as well.

That's normal... they use "boot" for trunk and "bonnet" for hood in the car manuals. (I remember seeing a glossary section showing translations in some of the manuals)

I went on UK ebay and the Haynes has a UK model pictured on the cover.



On USA ebay a similar manual can be found.



The contents are likely almost the same but if like the car versions the UK-version manual will have slight differences that show things like UK model ID information and the UK wiring diagrams as well as some of the pictures inside will be different. UK manual may or may not go over details like the "city lights" ignition switch that has an extra position on some UK models...

the Bottom manual is the one I have, that is a UK model 1975 DT250 on the cover.