Question about 2003 Yamaha YZ 125

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2000 YZ 125 Breaks up at High RPM. We think its the power valve. any tips would be great

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  • Cam
    Cam Jul 24, 2009

    we found out it wasnt the power valve so now we have nothing to go on

  • Cam
    Cam Jul 25, 2009

    We fixed it. It turns out it was a loose coil wire. when the engine would vibrate the coil wire would be on and off.

  • Cam
    Cam Sep 27, 2009

    It turns out the ground to the coil wire was loose.

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Check fuel float level as it might not be able to keep up the flow rate at those revs
or the read valve has become weak

Posted on Jul 20, 2009

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Hi kilroy,

below are links on all i got about the power valves, let me know if you need more information about it.

http://www.dansmc.com/powervalve.htm

http://forums.dirtrider.com/70/7724369/yamaha-dirt-bikes/93-yz-125-power-valve-problem/index.html

regards,

voodoo

Posted on Jul 20, 2009

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1 Answer

My 1999 yz 125 runs well at high rpm but won't idle and when I give it full throttle it bogs.


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
2. Faulty regulator/rectifier or high output coil.
3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
5. Cracked or incorrect float level.
6. Float needle is not seating.
7. Faulty reed valve.
For more information about your question and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
UPDATED 2005 YZ125 bog issue with videos
Dirt Rider Magazine
YAMAHA YZ125 Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

Jan 09, 2014 | 2003 Yamaha YZ 125

1 Answer

My 1999 yz 125 runs well at high rpm but won't idle and when I give it full throttle it bogs.


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
2. Faulty regulator/rectifier or high output coil.
3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
5. Cracked or incorrect float level.
6. Float needle is not seating.
7. Faulty reed valve.
For more information about your question and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals
OEM parts for Yamaha
YAMAHA YZ125 Owner Service Manual
Dirt Rider Magazine
UPDATED 2005 YZ125 bog issue with videos

Jan 09, 2014 | 2003 Yamaha YZ 125

2 Answers

99 yz 125 bog at high rpms


most likly needs new rings-or bad plug if you are lucky

Apr 28, 2012 | Yamaha Motorcycles

1 Answer

Yz 125 slow going into powerband


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
2. Faulty regulator/rectifier or high output coil.
3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
5. Cracked or incorrect float level.
6. Float needle is not seating.
7. Faulty reed valve.
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
1999 yz250 not hitting power band
YAMAHA YZ125 Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

Apr 10, 2012 | 2007 Yamaha yZ 125

1 Answer

Where can i get a manual for a 2000 yz125


Hi, Noisemarrine for more information about your question and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
Yamaha YZ125 service manual repair 2000 YZ 125 Download Manuals Technical
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals
Yamaha YZ 125 05
yz 125 tips and tricks YouTube

Aug 28, 2010 | Yamaha YZ 125 Motorcycles

1 Answer

What causes compression loss on a 1998 yz125? could power valve stick open or closed causing this? it was running fine and gradually has to be pull started. once i get it running it will not open up. it...


Pull started? on a YZ 125?
The power valve will not allow high RPM power if it is gummed up.
Low compression is due to bad rings, a different problem.
You may have both problems.

Jan 15, 2010 | Yamaha YZ 125 Motorcycles

1 Answer

2007 125 yz, has a miss before the power valve kicks in. short flat spot then , have keep the revs high to avoid it!!


There's no extra valve that kicks in to give the bike extra power. The term "power band" is simply referring to the RPM range of the motor that produces the most torque. Make sure the carb is clean and check the spark plug gap and fire. You need a hot blue,purplish fire not a weak white looking fire. If the plug itself is whitish in color you need to richen up the carb if it's black you'll need to lean it out. You should have a chocolate almond color. I'd bet the bike is getting too much air.

Aug 24, 2009 | 2003 Yamaha YZ 125

3 Answers

1984 yz 125 power valve how do i set it


You don't have to do anything It does it on its own as long as the pieces are all there. The power valve is the thing that opens up a larger exhaust hole for the two stroke engine. It is shaped like a spool and it twists as pressure builds due to high rpm. On the 1984 it is on the left side of the bike right up front behind the clutch cover.

Aug 04, 2009 | 2003 Yamaha YZ 125

1 Answer

My 97 cr 125 breaks up in high rpms like it has a rev limiter, it has a brand new carb and the cdi box, the power valve works fine. Could the stator do that?


hi this may help,it sounds to me like the carb is running way to lean,this may cause the bike to miss at high rpm,also check that the spark plug cap is in good condition as it may be breaking down under high load conditions...cheers

Aug 02, 2009 | Honda CR 125 R Motorcycles

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