The orange 250 is a '72 reed valve motor with the correct air box. The black RT has a '72 or '73 air box. It will interfere with the '70 or '71 seat pan. The air box for the '70 and '71 is smaller. I have a '72 air box in one of my '71 RT1B-360. Yamaha still makes the air filter element for the '72 and '73. I made a plastic lid for it that sits flush so the seat closes. Also installed a '72 battery box so I could fit the MotoBatt MBT6N4.

Alan

That "Pearl Yellow" bike is a 1972 DT2, not a 1971 DT1 (DT250 wasn't introduced until 1974). That might be your problem.

Regards.

Alan (yes, another one!) from Salisbury, UK.

Yes, it looks like you have a later air box... probably why it came without a seat.

It is important to ID bike correctly which is why folks get picky about it... Everything in the USA before 1974 used the old letter code and model sequence number.
F= ~50cc
J= ~ 60cc
G= ~80cc
H= ~90cc
L= ~100cc
A= ~125cc
C= ~175cc
D= ~250cc
R= ~350cc

Second letter T= "trail"
S or no second letter = "street only"

So if you have a DT2, no need to call out the displacement... DT2 = 1972 250cc Enduro or Trail model

Earlier Enduros used sub-letters up through 1971... For example CT1a, CT1b, CT1c... Then CT2 in 1972 and CT3 in 1973.

What makes this even more confusing is in the US, Yamaha used the same VIN prefix on many models through 1973... you need to use the full VIN to identify the exact model you have by using the VIN tables.

In 1974 the Yamaha marketing department decided to capitalize and promote the legend of the original 1968 DT1... considered the first "True" street/trail model by many... and started using the "DT" prefix for almost every enduro model... DT100, DT125, DT175, DT250, DT360, DT400, etc.

Of course there were many parts changes over the years... So very important to identify your model by the VIN and use it when asking questions... results in a lot less confusion for everyone.



Here's a post with a picture of what the lid of the correct box should look like...

yamaha-enduros.com/index.php/forums/1968...ox-in-a-71-rt1#25016

Attachments show all numbers off the bike as follows Engine and Frame numbers match Dt1f-115037, date 9/71 all found on vin plate on frame. Registration document found in the tool box along with the original tools, shows the bike was first sold in 72 and year model as 72. So is it a 1971 or 1972. Dt1 or Dt2. Confused I am. But hopefully not for long.

If you haven't done so already, you can check your VIN number against the table in the Tech Library on this forum (see top toolbar). This confirms that you have a 1972 DT2 in Pearl Yellow.

Yamaha tended to manufacture and date stamp their frames the year before the models actually went into production - hence a date stamp of 1971 on a 1972 bike.

Here in the UK, DVLA use the date on the frame when issuing age related plates, so that can sometimes mean that we get a letter relating to the year before a bike actually came on to the market.

Two different things here. "Model year" and "Calendar year".

Stamp on frame is the calendar date the bike was produced.

Most manufacturers of vehicles start producing the next model year in the previous calendar year. DEET probably knows exactly but Yamaha seemed to switch the line over to the next model year sometime in the middle of the previous calendar year... maybe as early as June or July?

This is not unusual or a "record"... I bought a first-year Dodge Neon in January 1994... it was manufactured in November 1993... But it was a 1995 model year

(Only new car I ever bought and truly hated... The good thing was the intro price was $9995... they had a very popular marketing campaign... remember "Hi"? ...anyway, they were sold out later in the year with massive waiting lists. Chrysler raised the sticker price a few thousand and dealers were adding thousands to sticker price... and still selling them faster than they could get them. I sold it back to the dealer for $14,000 a few months later. Worst car I ever bought but only new car I actually made a cash profit on!)

Thank you everyone for all your help. Now I think I know what I have and what I need to do. The information out there is amazing, Thanks again. Alan.

I don't know if a) the DT2 wiring harness is the same as my RT2 or b) I have already mentioned this but:-

1) Don't bother looking on the main harness for a white wire to connect with the one from the generator, as there isn't one (the white is basically a 'spare').
2) Don't connect anything, especially an earth, to the single black female ended wire that exits the harness from the generator about half way up - it is used to test the timing, points or suchlike and the bike won't run if an earth is connected.
3) Do fit a 6v voltage regulator if a previous owner hasn't done so already. Instructions are in the Tech Library under 'Service Bulletins'.