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Hesitation / Flat Spot / Surge @ 13000RPM

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by biceps, Aug 24, 2006.

  1. I dont know what the correct term is, and i have tried searching the forums but didnt get enough information.

    I just came home from a little 'fanging' session and notice there's a little flat spot that occurs at about 13000rpm. I have a honda CBR 250 R (MC19). There is a slight hesitation before all the power kicks in at about 14000rpm. There's no issues going from 14000rpm to 18000rpm.

    What could be wrong with my bike. I think it only occurs when i go for full throttle. It's less noticable if i gradually reach redline.


     
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  2. Is this a new problem? It is not uncommon for bikes (or cars for that matter) to have a flatspot somewhere in the rev range (could be due to the engine configuration or other various elements, e.g. inline 4s lacking any real power whatsoever below 6-8 thousand RPM). However if you know for sure that this is a newly emerged problem then that's a different story.

    If it's a new problem when were your carburettors last checked/cleaned? If it has been awhile then I recommend going and getting a can of carby cleaner and compressed air, dissembling the carbs and cleaning the passages, float bowls and jets with carby cleaner then blowing them out (in particular the jets) with compressed air. It's an easy thing to do (particularly so if you have the CBR250 service manual) and probably wouldn't hurt to do it anyway.
     
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  3. Im not too sure. I have a feeling this is a new thing. I only 'pushed' it a few times prior to tonight and it felt smooth everytime i did.

    I recently changed my fuel lines, fuel filter, oil, oil filter and opened up my airbox (just too see what was inside).

    I've only had this bike for about a month now. The only reason why i went for this 'push my bike to the max' session was to test my bike after my DIY service. I've also become more confident with the bike and hence, the only reason why i pushed my bike.

    Im not too confident with taking anything else apart (ie the carbs), so i might leave that to a mechanic. Does anyone know the cost of doing a service on the carbs?
     
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  4. If you are thinking about getting you're carbs serviced then I highly recommend taking off the fairings and removing the carbs then taking just the carbs themselves into the mechanics. This will save you a bunch on labour costs. But once you have gone that far you may as well clean them out yourself. It really is not that difficult if you approach it in a systematic way (take notes, take pictures on a digital camera, use the service manual et c etc).
     
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  5. I dropped the carbs off my ZXR600 down to my mechanic today to get done. It's costing me approx $80 in labour (I removed them from the bike) that's with everything in them now being sweet and not requiring new float needles (which are $50 each from Kawasaki :( )
    So I'd say anywhere round the $100 mark cause I'm going through a friend of a friend (both business owners)
     
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  6. biceps

    does the bike have stock exchaust system / slip on?

    maybe some other cbr250r owners can comment as this is maybe a model trait.

    if not either life with it or look at finding the problem. maybe start with a valve lash and as previously suggested a carb inpection and tune.
     
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