it may take a little time to resolve your issues, gut feeling is carb, does it improve with choke on, ie lose the induction roar of a non firing engine?
meanwhile....
DT175MX Ignition checks
There were two versions of ignition systems on DT175MX bikes. The mk1 version from the earlier bike had a 7 wire CDI the early bikes had a round section swing arm.
The mk2 version had a 6 wire CDI, the red wire is absent on these. These bikes have a square section swing arm.
The HT cap (AKA spark plug cap)
unscrew it off the HT lead, it is supposed to be a resistor cap so should be around 5K Ohms
The ignition coil primary...Orange wire to battery neg should be 1 Ohm +- 10%
The ignition coil secondary...HT lead to battery neg should be 5900 Ohms +- 20%
If the readings are much higher, check the ignition coil has a clean ground connection.
Yes and the ignition coil mounting is a wiring harness ground point too, so check its clean and bright there.
Disconnect all the wires from the CDI.
Then using your multimeter on the loom side of the connectors.
Black probe on a clean part of HT coil ground point
Red probe on......
Orange, Meter to 200 Ohms, expect 1 Ohm (HT coil primary)
Brown, Meter to 2k Ohms, expect 420 Ohms for mk1 and 300 Ohms for mk2 (Magneto charge coil)
White/Red, Meter to 200 Ohms, expect 12.4 Ohms for mk1 and 10 Ohms for mk2 (Magneto pulser coil)
Red, Meter to 200 Ohms, expect 13.6 Ohms for mk1 only. (Source coil 2 or high speed coil)
Black female connector, Meter to 200 Ohms, expect dead short
repeat for black male connector
Any difference in the results for the two black wires may possibly be rectified by cleaning the front engine mounting bolt and a little of the frame behind the bolt head, then tighten to torque spec.
Black/White, Meter to 20K Ohms, with ignition off expect dead short, with key on expect open circuit, with kill operated expect dead short (Engine kill operation)
If all these tests are good you would be well advised to try another CDI.
If they are not good...reading higher...disconnect and clean any plugs/sockets you find along the way, if the magneto coils are reading lower, new ones needed if more than 10%...or so the book says
Finally, if you are working with a box full of mixed parts!
Mk1 1 flywheel is Mitsubishi F3T250, it has two slots in the face of the flywheel
Mk2 flywheel is Mitsubishi F3T251, it has four slots in the face of the flywheel