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Carb issue Superdream CB250n Cafe Racer

This is a discussion on Carb issue Superdream CB250n Cafe Racer within the Technical forums, part of the Caferacer.net Forums category; Hallsie. Assuming you have a decent spark I'd check to see if the plug's wet. My guess would be a dodgy float, stuck float valve ...

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Thread: Carb issue Superdream CB250n Cafe Racer

  1. #11
    Senior Member steveo's Avatar
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    Hallsie. Assuming you have a decent spark I'd check to see if the plug's wet.
    My guess would be a dodgy float, stuck float valve or blocked pilot jet.
    You've been working on the bike for a few years now, when did you last clean the carbs?
    Might be a good idea to get them in a ultrasonic cleaner.
    If you can get the bike over to Colchester I could take a look at it for you.
    "It's better to keep your mouth shut and appear stupid than to open it and remove all doubt"

  2. #12
    Senior Member crazypj's Avatar
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    If you have 3 jet carbs, (highly likely) the only thing to do is re-fit airbox. The alternative is get hold of 2 jet carbs from a Canadian model. It's been done to death about the late model Honda 3 jet carbs,(1978~82) they were also fitted to CB750 and CB900 DOHC and are just about impossible to do anything with. Leon Moss, when he did carbs for Honda Britain and USA 'Superstock' blocked the primary main jet then re-worked the internals for the secondary mains. He ran a small bore tube inside float bowl for the pilot system. It was a ton of work. I can tell you whats causing the problems but have no idea how to fix your carbs, they don't respond the same as earlier CV as fitted to CB/CJ 250 / 360, The transition from primary main jet to secondary main jet causes a very rich mixture as slide starts to lift, if it were possible to lower the needle it would help a little as you need to lean out the transition
    Last edited by crazypj; 06-25-2019 at 06:20 PM.
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