Question about 2003 Yamaha YZ 125
2002 yz 125 push rod for the clutch is coming out. when I go to kick it, it jams up, but not seized up. pulled the spark plug, its flooded with gas and won't fire. Put it in gear and the bike tire will turn, but kicking it, it still won't start. can ya help @
Hi, Dave and the usual suspects are:
1. Fuel tank empty.
2. The fuel tank has old dead gas.
3. Fuel tank bottom contaminated with ethanol sludge, dirt, water, rust, etc.
4. Fuel supply valve/petcock turned off.
5. Fouled spark plugs.
6. Engine flooded as a result of overuse of the choke.
7. Vacuum hose to the fuel supply valve/petcock disconnected, broken, cracked, or pinched.
8. Fuel valve/petcock or filter clogged.
9. Fuel line to carburetor or throttle body pinched, kinked or blocked.
10. Carburetor float stuck.
11. Fuel injectors clogged.
12. Fuel injectors stuck open.
13. Quick disconnect check ball stuck.
14. Compression below 75 PSI.
15. A stuck-bent-burnt valve.
16. 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 cursory 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.
17. Check battery terminals for damage or corrosion, check the battery cables at "BOTH" ends for loose, corroded, or broken connectors, "INSIDE" and outside the cable harness, perform connector wiggle test and check cables with an ohmmeter if necessary.
18. Loose or corroded wire connection at the coil or plug between ignition sensor and ECM module.
19. Spark plug cables in bad condition and shorting check for spark leakage in the dark, cable connections loose, or connected to the wrong cylinders.
20. Ignition timing incorrect due to a faulty ignition coil, ignition module or MAP, CMP, CKP, O2, TPS, ETP, IAC sensors.
21. Faulty neutral, clutch, kickstand safety switch.
22. Faulty fuel pump or fuse or relay.
23. A stuck bent or burnt valve.
24. Tilt sensor needs a reset.
25. Security system not disarming alarm needs a reset.
26. Check for engine trouble codes.
27. Faulty run stop switch.
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.
yz 125 wont start
YZ 125 wont start
YAMAHA YZ125 LC Owner Service Manual
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Posted on Dec 03, 2017
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Posted on Jan 02, 2017
2 stroke bike are very dependent on compression. and being a bike that is 12 years old my best educated guess is that the top end needs to be rebuilt. i usually have to have the top end done on my honda about every three years.
Posted on Jan 13, 2009
Were you riding it when it jammed because that could mean the that something is sized inside the motor, like the crank or the pistion
Posted on Mar 30, 2010
two things come to mind firstly isthe machine correctly in neautral or have you picked up a flse neautral between gears if it is in fact properly in neautral tnhen I would be checking both the kickstart return spring & your selector mechanism
Posted on Apr 03, 2010
I agree with Rotax81 - it sounds like you're down on compression. Low compression will make a 2-stroke run rich and will make any engine increasingly difficult to start. What you describe sounds like the classic tell-tale signs of a shot top end, plain and simple.
I would not mess with the carb until you confirm the condition of the top end - it would be like putting a Band-aid on a broken Femur.
Posted on Mar 31, 2011
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