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Sick CB400

Discussion in 'Technical and Troubleshooting Torque' started by Jayce87, Sep 20, 2015.

  1. I'm hoping for any ideas or advice regarding problems with my CB400 as I have been looking for common issues online and all I can find is there isn't any. Before we start I have very little mechanical knowledge to fix much. My CB is a 2009 with 13,500 Ks on the clock and I have done the last 1,500 since purchase and its 12,000 K service.
    I have done a few rides around 2 hours but last weekend on the ride up to Noojee about 100 ks in it started surging under power to me it feels like on an older bike with no/low fuel.
    I ended up trailering it home and did a little bit of tinkering and couldn't figure out any obvious issues, however when I had the tank off I thought a vacuum hose was off and I wasn't sure if this had happened whilst I was taking the tank off. So this week I went out riding again staying closer to home and same again about 1 hour into riding same again but worse so bad this time it would idle but even in neutral a quick hard rev would just die.

    Anyway any ideas or information would be helpful, If you would like any more info just let me know.
  2. Oh also because I guess someone will ask i run 98 from a local servo when I can and only tend to fill up from well known servos when away from home.
  3. it's EFI not carby right?
    does it idle nicely when you are not giving throttle? but then dies under load or just neutral with throttle?
    can you very slowly increase rpm in neutral? if not, what rpm does it start dying?

    if it idles nicely with no load or throttle, then injectors are squirting in enough fuel, and ECU is telling them when to open correctly. and enough fuel is getting through the filter to at least support idle fuel neds
    dying under load could be many things..
    eg, filter clogged enough to prevent keeping fuel pressure at higher fuel requirement conditions
    ECU not getting right measurement of load (eg manifold pressure sensor, or throttle position sensor)

    or it might not be fuel at all, and either plugs are stuffed, or not enough spark power etc
  4. There was no consistency too it, at first it is only at high range in the vtec under power. however got worse an I noticed it kick in when the vtec did and perfect in neutral.

    However yesterday was worse and it was not at a specific rev range more when its past 1/4 throttle even in neutral and a very slow increase in RPM is better nut still problematic.

    It is fuel injected, and I assume one of the key points is that the bike is perfect for approximately 1 hour then just starts getting worse and worse.
  5. perfect for an hour then worse suggests it could be a heat build up issue, which could be fuel pump, or ignition or?

    if you let it cool down for half an hour, would it be ok again?
  6. Yeah it is perfect again for a while and then within an hour starts playing up again.
  7. I suggest either when it gets hot, you may have a split in a high tension lead that is arcing on metal somewhere and dropping a cylinder, or the fuel tank is not venting, and eventually the suction from the pump pulls all the air in the tank to vacuum and then it has trouble supplying the injectors, particularly under load. Make it happen again, and after a few mins of it happening, stop and immediately open the fuel cap.
    If you hear a suction noise, that may be the issue. I would also open the tank and start it straight away, then ride off with tank open (carefully) and see if the problem goes away.
    • Informative Informative x 2
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  8. Check the fuel filter first. Typical symptoms of a partially blocked filter.
    Also tank venting blocked as above by Tweet.
    Start with the simple stuff.
    Sounds like some form of fuel starvation, by your description.
    • Agree Agree x 2
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  9. #9 Ned, Sep 20, 2015
    Last edited: Sep 21, 2015
    Fuel filter is inside the tank with the pump, at least it is on this 2011 model I just renewed the fuel pump on with 27,000km. Pump was quite noisy.

    Also if you are checking the air filter it is the INSIDE that you need to look at, not the outside. Intake is down through the middle. Hope you get it sorted quickly.
    • Informative Informative x 1
  10. Thanks guys might be a job for next weekend now.
    I had the tank of the other day should have checked the fuel filter then.
  11. /\ /\
    As above, fuel filter and hoses, and then fuel pump.
    It might have a dodgy connection and dying when it gets hot.
  12. Exactly the same happened in a boat motor of mine - was fuel filter, but that was carby.
  13. Apparently I can't upload videos properly, but I have a video of what's happening, I think I will give in and find a local motorbike doctor
  14. Upload to photobucket or similar?