Yamaha DT 125 R - Recent Questions, Troubleshooting & Support - Page 9

Check fuses and battery cable connections. Check the attached links, "I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info." https://yamahaclub.com/forums/topic/31858-2003-dt125r-electricalindicator-relay-problem YAMAHA DT125R Owner Manual

Check the attached links, "I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info." Yamaha XT125 Carb Tips Mikuni 3D6 Mikuni Carb Series 3 assembly video with details Mikuni ucal carburetor pipes diagrams DT 125 Yamaha Google Search mikuni carb diagram Google Search

Is your bike a one volt bike or a 12 Volt DC biker?
1. What state is your battery
2. What state are your wirings from battery to coil
3. What states are your wirings in overall?
4. How are the wiring connections, are they all tightly connected?
5. Turn on your lights and see if they comes on bright or dim?
6. Press your horn does it sound solid or last breath?
7.If you can unplug your spark plug wire, put the wire about 5 cm from the spark plug tail and see if any sparks jumps, good idea to do it in a dimmed area.
This are just a minor checking indicators as many causes can be the source cause of your problem.

through experience i can tell you that dt125 r's are prone to warping heads and even barrels can distort at the studs.get the head and barrel back off and get them checked or skimmed minimally to be on the safe side,i would also leave the thermostat out.

how about replacing the fuse by the battery it is a master fuse and thats what it sounds like
since all lights and bike runs after a bump it sounds like a master fuse problem
if not check your batterie ground it might be cut or loose

All the Japanese bikes I have owned won't start in gear unless you pull in the clutch lever. There is a small plunger switch fixed to the clutch lever stock (the part that does not move). This switch is connected to the ignition and starter circuits, so when the clutch lever is closed the starter won't turn. Check the bike starts OK when not in gear. If you try to start the bike in gear and it does not start with the clutch lever pulled then the switch is not working. Hope this helps.