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CRF Carburetor Basics

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Hey guys, I have an '05 CRF250R.  I've been searching the internet trying to figure out how my carb works... not because it doesn't work fine (for now), but just because I want to know more about the bike and how to maintain it.  I understand the basic principles of a carb, allowing a throttled air flow which then draws fuel through the jet(s) for the right mixture.  I also understand the basics of fuel to air mixtures based on altitude.  So here are my specific questions:


  1. How many different jets are there?  Main jet, slow jet, leak jet, .... any others?  What is the function of each jet?
  2. How do you remove the jets for cleaning?
  3. How do you adjust the jets for different altitudes?  Is there a table or formula out there specific to my bike?
  4. How do you verify that your fuel/air mixture is appropriate?  How do you know if you're running too lean or too rich?
  5. Any other basic principles I should know?
  6. What should I be doing to maintain my carb?  Every time I put my bike away, I always drain the carb to prevent fouling.  Seems to have worked so far.  I've had my bike for 5 years, no carb problems whatsoever.  Anything else?


Any good explanations are welcome.  I'm an engineer, so don't be afraid to get too technical.  Thanks!

Edited by mitchkingkong

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Try to find your self the owners man. & competition hand book that comes with the bike when you buy it new, it will answer all your questions and much more, a great resourse for jetting adjustments and suspension adjustments.


Sorry, i'm a bad typer and just too lazy to answer all your ques. in detail , but you will be happy when you get that book.

Edited by bucket list

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