trying to locate an ignition switch with key for a 1973 yamaha DT1F 250 or information of another model that uses the same ignition switch. I am totally stumped. Thank-you in advance for any help

Sounds like you have a DT3 - compare your engine/frame number with the VIN tables in the Tech Library (see top toolbar) to confirm.

If it is a DT3, then the DT2, RT2 and RT3 use the same item. 

I have attached a couple of photos of the switch that you need. Make a note of the shape and the wire colours and terminals and don't limit your ebay etc search to just DT2/3 and RT2/3 switches, as many items get accidentally mis-identified.

  

Part # 275-82508-71-00 main switch assembly. Fits '71, '72, '73 DT1E, DT2, DT3, RT1B, RT2, RT3.

They pop up on eBay. NOS can be high $.

I hate to butt in but I have an ignition switch question. I have the ignition switch apart, a while back my red wire had come loose and I resoldered it, and now looking closer it looks like there's actually two connection points that it's soldered to, is this correct? Looking at the backside of the board it looks like they're designed to be soldered together, I'm assuming for when it's either turned on, or to the headlight position. I'm also assuming all that grease is correct to be in there. I'm redoing it because when I resoldered it before I didn't take the switch apart and I didn't do a very good job, I just want to make sure that that red wire is supposed to be soldered to both of those points that are right next to each other (right below the center point).

One other question, I'm trying to trace down problems with my turn signal causing the tail light to blink, it looks to me like the tail light bulb may have been replaced. What's in there now is T 1154. There is no marking whether it's 6 Volt or 12 volt, and looking online it looks like they're available in both, I'm wondering if a wrong one was put in. It doesn't look like the same vintage as my turn signal bulbs, that's why I think it's been replaced.

   
 

This picture shows the two connections right next to each other cleaned up, and I soldered another section of wire onto the red wire, with red heat shrink over it. I'm just not sure if it's supposed to be soldered to both of those connections right next to each other or not, but I kind of suspect it is. In fact they're so close together, it's almost impossible not to solder them together.

 

The diagram in the manual only shows one point for the red wire, it doesn't show two points bridged together, but it is between the brown on the right and the red and green on left.

I was wondering if because I had them bridged before, maybe that was causing my turn signal problem, or I may have had a little bit of solder bridging over to the brown wire next to it.

Oh well, I'm going to go ahead and solder the new red wire to both of those close points, and just be careful not to bridge to anything else, and see what happens.

 

 AH! I found a picture in an old thread and in this forum, and it shows the red wire bridging those contacts.

Industry number 1154 bulb is 6 volt.  Period.

1157 is most common number for a 12v version but there are other 12v numbers with different wattage and color specs.

In these days of imported junk anything is possible though. 

You're right Mark, I just went to AutoZone to pick up a 6 volt 1154, and 1157 is 12 volt version. The new bulb is actually a little bit brighter, but I still have my turn signal problem. Today today I've checked every single ground, every connection, the ground under the tank, put a new spade connector on the ground to the taillight. It just is not solvable, so I'll live with it. At least I got the red ignition wire soldered on better now. Actually the issue is a bit better now, in that the turn signals do work, but once I put the brake light on it seems to steal voltage from them and pulses for a couple seconds then gets steadier. As soon as I release  the brake, the turn signals go back to operating. Might just be a bug of 6 volt systems,  I honestly don't remember if my old one back in the day did that or not.

 
 

Too late for you now Tom (thank different time zones for that!), but I have previously posted a (pretty crap!) sketch of the ignition switch connections layout and can confirm that the reds are linked in what I called a "double". A link to one of my posts is below.

72 DT2 key switch wire diagram - Vintage Enduro Discussions (yamaha-enduros.com)

I would remove the grease, if you haven't done so already.

You're probably sick and tired of cleaning connections by now, but a dodgy one is still the most likely cause of your dimming.