Hi, Elbert_guian and the usual suspects are:
1. Severely discharged or a damaged battery should have 12.5 volts or more and be able to pass a proper "LOAD" test if necessary, you may have a preliminary reading of 12.5 volts or more but little or zero amperage the battery is faulty and must be replaced, AGM batteries fail in this scenario more so than lead-acid batteries.
2. Failed alternator/generator and or voltage regulator.
3. Loose or corroded battery terminals and or cables especially the "NEGATIVE" cable, look for loose, corroded, or broken connectors inside the cable harness at "BOTH" ends.
4. Failed main circuit breaker or ignition switch, check for loose connections and continuity.
5. Failed system and or ignition relay, check for continuity.
6. Failed ignition coil, stator, magneto, ignition/electronic module.
7. Failed CKP, CPS, CMP, MAP, TPS, or BAS sensor, corroded, loose or broken wire connector pins/sockets.
8. Throttle cables and or idle speed improperly adjusted hot idle speed should be 950 RPM to 1000 RPM.
9. Faulty neutral, side stand or clutch lever safety switch.
10. Faulty or corroded kill switch.
11. Accelerator pump damaged or not working.
12. Water or dirt in the fuel system, carburetor or filter.
13. Restricted, blocked or kinked fuel line.
14. Fuel tank empty.
15. The gas cap is not venting properly or fuel tank venting system blocked, loosen gas cap and go for a test ride.
16. A failed fuel pump, pressure regulator and or fuel injectors.
17. Vacuum line from intake manifold to petcock broken, cracked, or not attached, carburetor vent line plugged.
18. Needle and seat stuck closed in the float bowl.
19. Petcock clogged or damaged.
20. Lean angle switch is faulty or needs adjustment.
21. Catastrophic engine failure, perform a compression test.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below. Good luck and have a wonderful day. Rough Idle Then Stalling 2007 2008 Yamaha R1 Stalling Problem Fix How to Yamaha YZF R125 Service Manual https://www.partsfish.com/page/oem-parts-for-yamaha YAMAHA YZF R125 Owner Manual
Hi, Andrewjking this is Q&A website for motorcycle issues we do not sell parts or services. Please contact your local dealership or reputable repair shop for parts inquiries or go online for a parts supplier.
Good luck and have a wonderful day.
Hi, Sebkirk and the usual suspects are:
1. Fuel cap or fuel tank is not venting properly.
2. Fuel filter clogged.
3. Fuel line pinched or kinked.
4. Vacuum line from the petcock to intake manifold cracked.
5. Float needle and seat sticking.
6. Float level too low.
7. Carburetor bowl vent line clogged/blocked/pinched.
8. Idle adjusting screw set too low.
9. Air/fuel mixture screw set too lean.
10. Idle port, transfer ports, slow air jet clogged.
11. Slow fuel jet clogged.
12. Faulty fuel pump.
For more information about your issue and valuable "Free" downloads that you will need please Click on the blue links below. Good luck and have a wonderful day. YZF R125 Cuts out Help R125 150cc Idling Problems Yamaha YZF R125 Service Manual OEM parts for Yamaha YAMAHA YZF R125 Owner Manual
Hi, Kyle let me set the record straight about spark plug "HYPE" it's all "SNAKE OIL" Your bike when new came with a specific spark plug designed to give you maximum performance for the type of riding the bike was intended for. In my 60 years of riding motorcycles, the factory OEM spark plug worked the best. But what about the Multi Pronged-Platinum Core-Golden Tipped-Lazer Cut-Logo Etched-with exclusive patent designed LED cooling fins made in Hermetically sealed laboratories-packaged in Water Proof-Ballistic Transparent Thermoplastic Acrylic Plexiglass and endorsed by NASA that sells for the outrageously low discounted price of only $25 a piece you ask? Excellent question, these plugs only work in the Millennium Falcon. Seriously the bottom line in all these fancy plug designs claims may be true but it would take a team of Nuclear Physicists using classified electronic instruments to prove it. Regular folks like you and me would never see any difference. The temptation to spend 10x the cost of an OEM spark plug is great thanks to the highly paid wall street ad agencies, but trust me, save your money and replace your spark plugs with the ones recommended in your owners manual, if there was a better spark plug out there don't you think all the motorcycle manufacturers would use it? I have wanted to write this for a long time now my work is done, go in peace for all is right with the world. For more information about your issue and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day. Yamaha YZF R125 Service Manual OEM parts for Yamaha Yamaha YZF R125 Owner Manual Yamaha YZF 125 2009 Yamaha YZF R1 Wikipedia