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randymoore9 · Joined: 31 Dec 2008 Posts: 11

OK I have a DT1F engine, it has reed induction and CDI ignition.
Any idea what year it would be? Also cly. is 71.5mm is that standard or over size?
Only marking on the motor is DT1F no numbers?
Who is the Yamaha GURU?
Thanks!
Randy

shortyw7 · Joined: 09 May 2009 Posts: 3

Hi,your motor is most likely a dt3 250 maybe a dt2.Probably an enduro model but hard to tell without the other numbers.Could be an mx model but you need the rest of the numbers after dt1f to be sure but dt2mx models have a black cylinder and head and the enduros were silver and they also have a different stator than the enduros.ALL The dt's and rt models were stamped dt1 or rt1 on the frame and motors which really confuses a lot of people since a dt1,dt2,dt3 were all stamped dt1 on the frame and motor and the rt2's and rt3's were all stamped rt1.The easy way to tell if you have an actual dt1 or rt1 is if it does NOT have a reedcage.The dt1's and rt1's do not have reedcages.Another real easy way to tell if you have a dt1 is if it has tank decals or badges.Ony the dt1's and rt1's have tank badges that screw into the tank.If its got decals its a dt2,dt3 or rt2,rt3 unless someonee has changed the tank which then you can just look and see if it has reeds or not.Hope this helps you out:)

shortyw7 · Joined: 09 May 2009 Posts: 3

I forgot to add that i believe that is the standard bore.ALL of them were and still are great bikes and parts are readily available.Ride on!!

ken44yz · Joined: 31 Dec 2008 Posts: 39

I'm no Yamaha guru, but I have a DT-3 enduro(DT-1 engine). It has a mageto with points ignition std., 70mm bore std., so you are 1.5mm over if in fact it is a DT-2 or 3(same). Not sure about the std. bore or ignition on the '74 model, called the DT250. That engine is different from previous years.

holat88 · Joined: 15 Oct 2009 Posts: 34

The DT2MX engine prefix was DT1F, had a blister on the clutch cover where the earlier DT1 shift shaft went thru (splined on both ends) and another possible giveaway is that the DT2MX head and jug were basically square with no head fin cutout on the right side while the Enduro models thru 1973 were the standard tapered fin jug with the cutout head fins for the left side exaust. I have a brand new left side engine case w/out a complete serial number but it does have the prefix DT-1F and came in a package marked with a factory Yamaha label 322 prefix (DT2MX 1972).
Strange but not unusual.

perryhayes · Joined: 20 Feb 2009 Posts: 94

If it has a CDI unit it's probably a 72 DT2 MX.

odaat · Joined: 31 Dec 2008 Posts: 50

The true 72 DT2 (250) MX had a one year only uniuqe points, condenser and an internal lobed rotor as standard ignition and reed cage. The 72 RT2 360) MX was the first year of the non dependable CDI ignition with internal rotor....all of the enduro 71,72,73 DT's and RT's have points, condenser and huge flywheel as standard ignition, 72 and 73 units also had reed valve intake. Sorry, but I don't have my spec book here for bore specifications.

fjr121693 · Joined: 05 Feb 2009 Posts: 12

DT2 1973 250 DT2 Dual Purpose DT2 DT1F-105101

Hope this helps.

perryhayes · Joined: 20 Feb 2009 Posts: 94

bradyup1 · Joined: 31 Dec 2008 Posts: 10

Hi Randy, the DT1F with reed valve came out in 1972 known as the DT2MX, the CDI came out the following year (1973) as the 250MX or DT3MX, the RT2MX and RT3MX both hade CDI's. A DT1 is a 250cc (ie the enduro), but the DT1F is the DT2MX, although with a CDI that is a little strange. Now maybe it is possible that the very late DT2MX had a CDI, but I have owned 2 DT2MX's as well as my best friend who had one, and I know they had points cause I always got stuck setting our timing on our bikes. I have also owned the DT3MX (aka 250 MX) and a RT2MX, both also had CDI's. You may want to look at some photos of the DT2MX motor verses the 250 MX...the cylinders and side cases look a little different. And I don't know if you have the pipe, but the DT2MX exits on the right side while the 250 MX (DT3MX) exits on the left side. Good luck Randy..Google the DT2MX...sounds like a very late 1972 DT2MX(?) or a 1973 DT3MX??

perryhayes · Joined: 20 Feb 2009 Posts: 94

The 72 DT2 MX and the 73 MX 250 engines are totally different. The DT series of Motocross bikes ended in 1973. The RT series of Motocross bikes ended in 1972. The DT1 /RT series of Enduro models ran through 1973.
In 73 you had the 250 and 360 MX, and the DT3 Enduro and the RT3 Enduro. In 74 it was the 250/360 MX and the DT250 AND 360 "A" models and of course the 74 YZ 250/360 A who's engines where based off the DT1/RT engine until 1976.