No spark on yamaha dtr 125cc

pull cover on magneto and check for loose pickup coil.

Yep, clogged fuel filter, dirty carb. ????

Hi could be the kill switch wiring

The TTR-125 Carburetor's Run Lean by design. Mine had the same issues till I found a post on Thumpertalk.com on Carb and air box Mod. This is a good starting point on gets; 110 and 112.5 main and 17.5 pilot. But you must check spark plug coloring to make sure the jetting is correct. Check spark plug after the bike has been ridden for a wile. I also took out the stock baffle and replaced it with exhaust tip and now it fires up after a few kicks and worms up in a few minutes.

Check the wiring exiting the crankcase up to the rectifier/CDI unit and ignition coil. Look for excessive squashing, pinched or burnt (very stiff) wiring. Check all connections are firm and free of corrosion. Ensure plug lead is not arcing to frame or engine when in place. Make sure ingition coil is FIRMLY earthed at mounting point. A good tip is to run an earth wire from the head bolt to the frame. Thoroughly check any "kill switch" wiring as moving handlebars, throttle cable etc whilst kicking over may interupt electrical circuit. It is common for wiring to eventually get caught up in the steering "stops" on the lower fork clamps, cutting or severely damaging wiring. The wires exiting the crankcase come from the generator and without a rotor puller they will remain unsighted behind the generator rotor. You can easily remove the cover however, and check grommet where loom enters for pinched or flattened wires.
Check the site below (scroll down for your Model/Year) It has exploded view diagrams of all the pertinent parts to see your bike going again. Cheers.

http://www.cmsnl.com/yamaha-motorcycle_model16707/

hummm check your electrical connections make sure you have the stop run switch is in run position,you have fuel flow to the carb, make sure you are getting spark to the spark plug by using a extra spark plug remove the plug cap and ground it to the head and kick start the engine and see if you are getting spark to the plug.
hope this helps

MAKE SURE YOU HAVE SPARK AT THE PLUG
MAKE SURE YOU HAVE COMPRESSION
REMOVE PLUG PUT FINGER OVER HOLE AND KICK
IF YOU HAVE BOTH OF THOSE TRY CLEANING THE JETS IN THE CARB

Go on ebay and buy a new CDI computer those bikes are notorious for computer failure.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/brandon_79b580f5a99c4386

well at first in wont fit because the cooling (LC) system will not fit the 02, but with a little welding and some alum works, you will be able to fit it.

the only difference will be the placing of the mount, weld holes and drill holes on the frame, but before you do so, remove all electric components from the frame.

hope this helps.