Question about 2003 Yamaha YZ 125

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2001 yamaha yz80 backfires and wont start

We replaced the stator and put a new spark plug and Carb. The bike just backfires after several kicks? The spark plug is wet each time we check. Is there some kind of timing issue? The piston is definitely getting spark?

Posted by Anonymous on

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  • Yamaha Master
  • 40,627 Answers

Hi, Anonymous and the usual suspects are:
1. Severely discharged or a damaged battery, should have 12.5 volts or better and be able to pass a load test if necessary.
2. 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.
3. Faulty main circuit breaker and or connections.
4. Faulty ignition coil and or connections.
5. Faulty spark plug, oil or gas fouled, wrong heat range or service type, wrong gap, loose in the cylinder head, broken electrode or insulator.
6. Faulty spark plug cables, leaking or broken, internal damage.
7. Faulty ignition module, switch, CKP, MAP, CMP, sensor and or any connector in the ignition circuit could have corroded, loose, or broken pins/sockets
8. Burnt exhaust valve or air leak in the exhaust system.
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.
Bike won start just backfires occasionally
01 FZ wont start after back fire FZ1OA Message Board
Yamaha YZ125N1 Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

Posted on Jul 13, 2016

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Posted on Jan 02, 2017

Benimur
  • 6966 Answers

SOURCE: YZ 450 STARTING PROBLEM

Hi and welcome to FixYa,

Offhand, the backfire is significant. It indicates that fuel is getting inside the combustion chamber and it further confirms that there is spark. Being the case, it would appear that this is now a timing issue. A couple of ideas to explore:

  • compare the original stator coil and the uprated one; are the coil location on the same side, on the same angle, on the same distance from the edge;
  • there would be a guide notch on the base plate of the coils, are they identical and does it fit exactly back into position;
  • there would be a guide/lock pin that keeps the magneto/flywheel in position;
  • there would be timing marks on the magnet/flywheel that must coincide with marks on the engine case.
Good luck and Thank you for using FixYa. Happy Holidays.

Posted on Dec 15, 2008

  • 1 Answer

SOURCE: yamaha yz125 wont start...

hello there guys, listen a top tip is when the engine's cold tip the bike almost right on its side nearly touching the floof, wait for the petrol to poor out of the carb over flow pipe, this should take a matter of a few seconds, stand the bike back up again and kick and that baby should start right up, if it does then you have a problem with your float, if it still doesn,t then take it to a shop and get them to check it out, hope this helps. regards sam

Posted on Jan 24, 2009

  • 3 Answers

SOURCE: i have a 2000 yamaha wolverine it won't start

it sounds to me like your bike has shorn a flywheel key. and is sparking at the wrong time.

Posted on Feb 11, 2009

  • 3567 Answers

SOURCE: yamaha yz80 wont kickstart

There is a "C" clip with a stem at a right angle as a part of the clip. This is a part of the kick starter mechanics. Replace the clip. It is about one inch in diameter.

Posted on Mar 12, 2009

  • 3 Answers

SOURCE: i have 1974 yamaha dt 250 enduro the bike sat

clean contacts on points with sandpaper (800 grit). located behind flywheel, will gurantee a fix. you can remove the side cover and get to contacts through holes in flywheel without removing it.

Posted on Nov 16, 2009

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Did you line up the stator plate line with the notch on the cases? Sounds like your ignition timing is set a bit retarded. I would pull the side cover off and check the timing marks.

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I have a 2001 yz80. The spark seems weak. I tested the coil and its fine. I tried it with the kill button disconected, it didnt help.How do I test the stator and cdi? Am I on the right track?


yes buddy the only way to test the cdi is too put on another bike and if it was the stator it wouldnt spark and yes you are on the right tracks but maybe it could be the plug does it run brilliantly

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Yamaha yz125 wont start...


you should try cleaning your carb i dont know how often you clean your air filter but if you havn't done that you should do it also.after you do that turn the gas on lean it over till gas runs out the over flow and give it choke no gas and try kicking it over.you should be able to just loosen up the clamps on each side of the carb and twist it so you can get to the float bowl,unscrew the four screws and blow it out with a air nossle you can try that before you go through the troubles of taking it off to clean it.

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