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Troublesome ZXR250a

Discussion in 'Technical and Troubleshooting Torque' started by 4lex, May 8, 2006.

  1. My ZXR250a is giving me the shits. It's been running rough for some time, so I finally bit the bullet and took it in to have the carbs overhauled. The guy has stripped and thoroughly cleaned them, and done a vacuum balance and says they're in reasonable order.

    We found out that the bike had no fuel filter fitted, so have fitted an inline job, plus each carby has a tiny gauze filter, which are now all clean and should be flowing just fine.

    One problem is that the gaskets on the top of the carbs, under the airbox assembly were unavailable, so these are on order, but I figured it should run ok without them in the interim.

    Thing is, the bike now runs worse if anything. It starts just fine (easier than before), but opening up the throttle, particularly under load, the motor seems to bog down and doesn't pick up properly until about 10-12k rpm.

    One suggestion is a failed HG, but there's no excess steam in the exhaust or loss of/cross contamination of oil & coolant.

    What could be the cause? I'm planning to strip the plugs out & clean/replace and check all the leads are working properly this evening, but failing that I'm at a loss for what to do.

    Any ideas?

  2. The diaphram gasket could well cause this problem.

    One of two things could be happening:
    1. the slides are sluggish to come up
    2. the slides are coming up too early.

    also if the idle screw was set incorrectly or the needles were put back in the wrong place, then this could also cause problems.

    Or, the float levels may be wrong. It's not hard to give these modern carbies too much fuel, through float level problems.

    I wouldn't be thinking head gasket or similar yet.
  3. simple if the air box is not on properly... ie the gaskets b/w the air box and the carbs are not working.. than the bike will get to much air and make it run like an old bag at high RPM... oddly it will start easier :) as it it will not be flooding like these bikes normaly do...
  4. Thanks mate. Diaphragms was the next diagnosis from the guy who did the carbs, he didn't get the opportunity to test ride it as he'd squeezed the job in for me on a sat AM. Going to drop it back tomorrow for another go, though I'll still have a nose around the electrics this eve.
  5. Nah, it runs great at high rpm... its low & medium not so great...

    I see in your profile you've got a busted ZXR250a? I could use an o/s pillion peg, tail lamp and the rear piece of fairing that surrounds the tail light, if you're willing to part company with any bits?
  6. Well the bike is in such a good condition besides the engine... I would be willing to part with the WHOLE bike as is... or fix/replace the engine and then sell it...