Question about 2003 Yamaha YZ 125

1 Answer

I was riding my 2003 yz125 and it stalled since then i have not been able to kick start the bike i checked the plug and its getting plenty of spark i put a compression tester on it and its reading 150 psi so its not a compression problem i can push start it and it will run fine as long as you are on it but if not it will just stall out what could the problem be?

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  • Yamaha Master
  • 59,811 Answers

Hi, David 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. 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, 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. Air/fuel mixture screw improperly adjusted.
10. Accelerator pump damaged or not working.
11. Water or dirt in the fuel system, carburetor or filter.
12. Restricted, blocked or kinked fuel line.
13. Fuel tank empty.
14. The gas cap is not venting properly or fuel tank venting system blocked.
15. A failed fuel pump, pressure regulator and or fuel injectors.
16. Vacuum line from intake manifold to petcock broken, cracked, or not attached, carburetor vent line plugged.
17. Needle and seat stuck closed in the float bowl.
For more information about your issue and valuable "FREE" downloads that you need please click on the links below. Good luck and have a nice day.
yz 125 wont start
98 YZ 125 won start
YAMAHA YZ125 Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e

Posted on Aug 01, 2016

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6 Suggested Answers

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Posted on Jan 02, 2017

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Anonymous

  • 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

tombones

  • 3567 Answers

SOURCE: VERY hard starting takes way to many kicks usually play out befo

There is a proper way to start the engine. Four controls are on your bike to assist in starting.

  • The choke, used when the engine is cold. Pull the red knob for choke.
  • The " Hot Start " Lever, used when the engine is hot. Pull the lever to lean the fuel mix when the engine has been running.
  • The de-compression lever, always used.
  • The throttle, used to prime the cylinder.
Don't kick, instead, push the kick lever downward. You will feel the back pressure as the piston is going upward on the compression stroke to the point the pressure is great enough that the kick lever "locks up". You are very close to TDC. NOW, pull in the de-compression lever. Push the kick lever a little bit more to get the piston past TDC. Release the de-compression lever. Give the throttle a 1/4 turn then let it snap closed. A diaphragm in the carb gives a shot of gas when this is done. DO NOT do this multiple times because you will flood the engine. Leave the throttle closed when kicking. Give a strong kick through the full sweep of the kickstart lever. Quickly get your foot off the kick lever at the end of the kick to avoid any chance of "kickback" from a backfire. It can be very painful, and can even break a leg. I am serious about that. Repeat the process (but without the throttle priming), until the bike starts. A good battery, a clean spark plug, a clean carb and clean air filter will also aid in starting.

Top rating for this answer? Thanks!

Posted on Jun 11, 2009

bozcro

bozcro

  • 867 Answers

SOURCE: Thanks for all the tips on this CRF250R Honda but

i dont know what all you have tried so far, but check the fuel filter, usally in the tank above petcock. the compression seems fine as you had to bump start it in third gear. you can feel the compression of a bike when pushing it in gear, like a bike with bad compression you could push in first without wheel locking

Posted on Sep 10, 2009

Testimonial: " lots of gas , injector cleaner in the gas, spray cleaned up carb in frame,pulled of valve cover cam looks burnt blue in colour lack of oil? valves "

Anonymous

  • 1 Answer

SOURCE: Stalling out, when not completely upright

My 2003 has a cutoff switch on the kickstand.

Posted on Oct 11, 2009

Fabrice Wolters

  • 331 Answers

SOURCE: i have a 1974 dt 250 same as an dt 360 the bike

Compression is too low!

Replace the piston rings.

Also check continuity from engine to frame till high-tension coil...
Check if breaker points aren't dirty ( clean out with fine sandpaper )
Check breakerpoint settings

Posted on Nov 01, 2009

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Its quite a brief description of issue but any way I assume it is not starting???

You need 3 things to have a running motor 1 Spark at plug test this by removing plug connecting it back to the plug lead lay it on motor and kick bike over to see or not the spark, 2 fuel getting through to spark plug... test this by smelling and feeling the spark plug immediately after kicking it over should be wet and strong fuel smelling... 3 compression there are special tools for this but a simple back yard test is remove spark plug put your finger or thumb over the hole the plug came out of and gently kick bike over if your finger is not forced off instantly and you can resist some or most of the pressure when kicking it over then you have nowhere near enough compression...

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2003 yz125 wont start


Not much info to go by, but i'll give some things to check. Got fuel? Got Spark? Got Compression? If you have all these things, after kicking several times, pull plug to see if the plug is wet. If wet dry with compressed air, ground plug on head bolt or use spark tester, Kick engine over while watching plug, it should spark. If not replace and try again. If still no spark, check kill switch with ohm meter to make sure is working properly. If still no spark you will have an electrical issue with either the CDI Box or Stator. If the plug was dry without fuel, pull fuel line from carb. check to make sure fuel is running, if not check fuel shut off valve. sometimes the shutoff valve will clog up. If all is well it has to be a clogged carb.. Good Luck

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check the compression with a compression tester. you may have burnt the ring out on the piston. if you don't have a compression tested you should buy one and test is right but if you remove the spark plug and stick your finger over the hole while you push the kick starter down it should force fully push your finger off. if so you have compression if not then you don't have compression and need to redue the top end.

if you have compression check for spark by taking the plug while it is still out and plug it back into the wire and rest the tip of the spark plug or side of it on the head and push the kick starter again. you should see the spark plug spark at the tip. if so it's good and if not you may have a bad coil or something in the ignition system.

but check that and et me know and i can further assist you.

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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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