At Fixya.com, our trusted experts are meticulously vetted and possess extensive experience in their respective fields. Backed by a community of knowledgeable professionals, our platform ensures that the solutions provided are thoroughly researched and validated.
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
You should really have the workshop manual if you are working on the carb. Not only will this tell you the correct main jet size, you will also get the pilot jet size, mixture screw, and jet needle positions. All of these should be checked if you're taking apart the carb yea?
The above site has all info for a 2008 model. Compare with 2006 model on same site for descriptive differences of major components, and specifications. Torque settings etc. are generally bolt type specific, ie; The bolt size it self determines settings, this should be outlined in your Haynes, using the bolt size code (usually stamped on head of bolt) transfer to your newer model. Yamaha owner's manuals can be viewed on-line or at public libraries for a comparison for model updates etc.
It's likely just jetted too rich. If you pull your spark plug, it will likely be black and oily. To correct this, you need to alter your jetting. Jetting is not an art - it's fairly straightforward - you just have to physically change the jets inside the carb.
There are only two adjustments to make on your carburetor; the idle speed, and the idle mixture adjustment. If the spark plug fouls frequently, first make sure you are using the correct spark plug. Your 1997 YZ125 uses an NGKB9EGV. Then be sure you are using the recommended two stroke oil, mixed to the proper ratio, in the fuel. Also make sure the air filter is not excessively soiled.
With all of the above confirmed and corrected, start the bike and run until the engine is up to normal temperature. Adjust the idle mixture screw to attain the fastest idle and best throttle response. Then adjust the idle speed.
If you are still fouling the spark plug, verify that the carburetor has the correct size jets by consulting your owner's manual. Keep in mind that if you are operating your bike at an altitude higher than about 6,000 feet above sea level, the stock jetting may be too rich. Down-size the main jet in small increments until satisfactory operation and the correct spark plug color is obtained.
×