Question about 2004 Yamaha YZ 125
Hi, Lissahere and the usual suspects are:
1. Fuel tank empty.
2. Fuel supply valve/petcock turned off.
3. Fouled spark plugs.
4. Engine flooded as a result of overuse of the enricher.
5. Vacuum hose to the fuel supply valve/petcock disconnected, broken, cracked, or pinched.
6. Fuel valve/petcock or filter clogged.
7. Fuel line to carburetor or throttle body pinched or kinked.
8. Carburetor float stuck.
9. Fuel injectors clogged.
10. Severely discharged or damaged battery, you need 12.5 volts or better and be able to pass a load test if necessary.
11. 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.
12. Loose or corroded wire connection at the coil, battery or plug between ignition sensor and module.
Spark plug cables in bad condition and shorting, cable connections loose, or connected to the wrong cylinders.
13. Ignition timing incorrect due to a faulty ignition coil, ignition module or sensors (MAP, CMP, CKP, O2, TPS, ETP, IAC,or BAS).
14. Faulty neutral, clutch lever, or kickstand safety switch.
15. Faulty fuel pump or fuse or relay.
16. Faulty CDI box if applicable.
17. Tilt sensor needs a reset.
18. Security system not disarming alarm needs a reset.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
Dirt Rider Magazine
yz 125 wont start
YAMAHA YZ125 Owner Service Manual
OEM parts for Yamaha
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Posted on Jul 19, 2016
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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
Posted on Mar 23, 2009
Pull the carb off the bike and clean it inside and out. Be sure main jet is clear. Remove the two screws on the outside throat of the carb and spray into the screw holes as well. Be sure to put these two screws back in the same hole they came out of. IMPORTANT > > > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward.
Put the rest of the carb back together and install the carb. Turn the gas on to let the float bowl fill then start the engine. Chances are this will fix the problem. I suggest that you install an in-line fuel filter to prevent this happening again.
Last item> You should have just a little bit of slack in the throttle cable where it goes into the top of the carb. Not more than 1/16". Let me know how things turn out.
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Posted on Mar 28, 2009
You have a 50/50 chance that they will work okay. All the mounting holes need to line up and the cooling holes as well. Get a head gasket for the '98 and see if all lines up. Will the exhaust pipe fit the '95?
Posted on Apr 30, 2009
You know aluminum can be welded very successfully now, so best bet is to remove that case and take it in to a good welder..You can ry the quick fix (JB Weld) is what i recommend, but success is rare !....good luck to you my friend...Tim
Posted on May 10, 2009
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