I've posted a similar question as a follow up on another thread. 
here's what I got..

I've completed the engine build for a 75 dt250. (Only engine, no bike). What remains is the electrical/ignition setup. 

I've bought several (as I come to find out) wrong parts for a points dt250b. I have a 74 dt400 flywheel which I thought was the same as a dt250b but the dt250b worked off a points ignition and my dt400 flywheel doesn't have the eliptical center hub needed to work points. 
My stator plate is correct for the engine being a FOTO19. I ordered the source coil but the coil only fits where the charge coil fits (the RH side). The ohm reading is 1.6 which matches the requirements in the book. I've also got a new set of points and condenser.

Now to my question. If I buy the CDI/stator plate/pickup will it work with my dt400 flywheel on this dt250?

Or do I need to buy a dt250b flywheel? If so will the coil on the RH side of the of the stator plate work to give me the spark I need to get this fired up?

I'm obviously not working with unlimited resources so I'm trying to figure out the least expensive way to move forward given what I already have.

Thanks for the help a head of time.

Zack

Sorry to hear ya not having an easy time of it. I'm 'as sure as i can be' that a 400 cdi mag will bolt straight onto a 250 complete with flywheel. "78 DT400 is a better mag & "79 DT250 also went cdi if you can find one. Those earlier systems the pulser coil gave bother--but if you find a good one--then good!!.. I had one of those later systems on my old RT2 race bike & never faltered. Hope others with more knowledge than me get involved soon. Cheers from NZ. ps, an RT2 is an older 360 motor up to "73 or 250 of same era.

If your coil is not on the correct side of the stator, it may or may not work...  that seems really odd so it might not be the right part.  As it was said in your other post, you'll just have to try it.

The rule on the 250/360/400 ignitions is from 1974 to at least 1979 they are interchangeable as a matched set.  You can't mix and match parts.  Whatever stator you want to use, you must use the matched flywheel for that stator.  (as you've already found out)

This is definitely true for CDI versus points...  and may also be true for ignition models.  A 1975 points stator may not work with a 1978 points flywheel if the ignition model or brand was changed between those years. (Yamaha tended to switch between Hitachi and Mitsubishi systems)

It might be worthwhile to look at a VAPE/Powerdynamo if you can't find what you need...  or just keep your eyes open on ebay for used systems. The problem with the Yamaha CDI's is they are expensive and many have failed.  You'll also need the correct DT400 CDI box if you find a CDI stator to go with your flywheel.

I stuck in the same problem. Had an ignition working not reliable. Brought another stator on Ebay,  but slightly different. Worked somehow,  but ignition coil was faulty and kept my busy for Month until I found out. Mark is right. Buy a Vape conversation kit . Somebody said it to me 2 years ago and I didn't.  After all I know now,  I should have done right from the beginning.  If you sell all components you have right now on Ebay, it will compensate partly the Vape price  and your problem is solved 

Mark,

Thanks for the reply.

I'm curious about the CDI systems and how/what could be different between 4 magnet flywheels. If the CDI replaces the points opening and closing visa vi pick-up coil couldn't you just use a modern CDI say from a Yamaha blaster?

Great info guys. Thanks!!

Blaster base plate is only 120mm diameter (yours is 130), bolt pattern different, and flywheel taper is different.  Some other issues but those are the biggies. 

If you could find a modern CDI that fit, yes it would be okay.

And if you're thinking of mixing and matching parts somehow you could get lucky but as simple as they look there is a lot of engineering in the magneto.  Exact coil placement, air gaps, and a lot of details have to be pretty precise or no spark

I'm leaning towards getting a dt400 CDI with maybe just the charge coil on it, I've got the right flywheel for it and after looking at my part numbers the coil that only fits into the right hand side of the stator will fit in the left side of a dt400 stator plate.

Hopefully it will have a good pickup coil on it and I'm going to try to run it through an aftermarket blaster CDI.

I'll check my currents and God from there.

As far as the Vape systems I see 2 that sound right.. a $400 one and.a $600ish one. Can anyone tell me which one I should buy if this plan doesn't work?

1975 dt250b

Also the autolube system should work. When first getting it started should I just use mix? Can I run it without oil pumping through the pump,?

Last thing is I have a 28mm Chinese carburetor. I planned on using this for starts? I've had good luck with them on my blasters as they also call for a 28mm 2 st carb.

Remember guys im not even sure what I'm going to put this in yet when/if I get it running. Either a blaster frame or a '89 ninja250 frame... Obviously seriously modified. So let's keep the $ at a minimum if u can.

I've had a system running on a DT125L using just the cdi source coil & a secondary plug coil cdi box combined of a suzuki rg50 or other small suzies like jr50 etc. Worked good & a simple setup with no trigger coil to worry about. Did have my IT200 running as normal using a points flywheel over the cdi stator plate. Had to time it without the crank key after strobing with wife turning the back wheel to find the firing point to then set the crank-piston at whatever, 2mm btdc probably. Was years ago but used it for a long time before selling. Bought it as a wreck with no flywheel or carb. Flywheel was of an RX125 so left side flywheel on right side IT motor. Amazing what works when can't locate the correct flywheel.

So wait you had a points flywheel and a pickup stator plate with no pickup coil?? How did the coil know when to fire???

That is quite the creative way to get a spark.. I've got the opposite, a points plate and a CDI 4 mag flywheel. Thoughts on my application would be greatly appreciated!!

No, i had a points flywheel on my IT200 so was an original stator with points flywheel but the cam did nothing, so magnets fire the trigger-pickup as original. Was just lucky it fitted although had to machine the flywheel overhang back to the magnets to have clearance against the stator & also time it without the key. Did it up very very tight & never slipped.
But my other DT125L water cooled had a destroyed pickup coil from lighting coil screws coming out, So 'that' one i used the Suzy coil box combined. They don't run a pickup--call it pulser coil & fire by magic somehow when i guess the magnets go past the end of the source coil. Probably no different to my lawn mower, no points & just a coil, but is a coil box combined. Sorry if i talk in riddles at times. Have no advance or timing variation capability, just firs at whatever you set it at. Funny thing 'is' on 'that' one--the 125 i thought i might need to time it without the crank key & do it up damn tight but strobed it kicking & was ok secured by original crank key so nothing changed--lucky on that one. Common small bike suzuki ignition system where no real timing changes are needed for optimum performance. In saying that i guess an RG50 is a high revving little go'er. So i don't know.
Source coil on that was about 350 ohms which is normal for that type of system.