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Honda CB250 running issues.

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by jackm, Oct 11, 2016.

  1. Hey guys,
    I am having troubles with a 1983 Honda CB250 that i have just purchased. For the first 15-20 minutes of a ride the bike will not rev up above 2000rpm, but then all of a sudden it will just start running really nicely and rev all the way through??? I'm thinking this is a carb or electrical issue but have no idea.... Has anyone ever had a problem like this before or know what it could be?

  2. Does the bike start OK, even when cold? That would rule out the choke. I'd say you have a blockage in the fuel lines, or one of the breather tubes and the 20min ride is enough to soften the rubber a little to stop the blockage. That's my best guess anyway.
  3. Yeah it starts up straight away every time. Ok thanks, the lines seemed to be fine, but I will double check now.
  4. Nope... they seem to all be clear...
  5. What is the exhaust like during the 20 mins of poor running, clean, smokey, steamy?
    Are both cylinders firing (both exhaust headers equally hot)?
    What do the spark plugs look like during the 20 mins poor running (wet/oily/dry/black/tan/white)?
    Is it missing during the 20 mins poor running, or are both cylinders firing well?

    To me, it sounds like the warmth of running finally dries off something causing an electrical issue with the ignition or similar.