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CB250 sluggish now not starting

Discussion in 'Technical and Troubleshooting Torque' started by Layzie, Jan 6, 2016.

  1. #1 Layzie, Jan 6, 2016
    Last edited: Jan 6, 2016
    Hey guys. My Honda CB250 started up this morning and as soon as i left my house, the bike seemed very sluggish and the idle didnt sound right. The bike seemed like it was struggling to accelerate so i rode it back home. Now the bike doesnt want to turn over. I know its not a battery issue. What else could be the problem?
    I checked the spark plugs and the tip looks all black. Could this be the issue?

    I did notice that it was 'sort of' idling fine when i put the kickstand back on and leaned the bike. But not when it was upright.


  2. So i replaced the spark plugs and the bike seems to be running now. Took it for a 10min ride and didnt have any problems HOWEVER i noticed when i turn the handlebar to the right, the idle drops and gets sluggish again but goes back to normal when i straigthen it.
    I did some research and people have been saying that it could be the throttle cable either too loose/tight. I havent made any adjustments or changes to the throttle cable or the cables around it. I went to check the throttle cable and moved the handlebars left/right but i didnt noticr any tension or slack. Theres a possibility that its getting squashed by the steering lock/stopper when i turn it to the right?
    Any tips/help would be much appreciated.
  3. Plugs are pretty fouled. Appears to be running very rich. This could be causing running and starting issues and at best you won't be running efficiently.

    How long since the bike has had a tune up and new plugs and air filter? If not for a while I would try that first and see if things improve.
    It is also possible bike is running rich due to incorrect carby adjustment. CB250 is single carby so relatively easy to adjust the mixture if that is the problem but I would be trying a replacement air filter and plugs first .

    On the upside I would never worry abut a CB250 running sluggishly. That is what they are designed to do :p
    • Like Like x 1
  4. OK Just saw your new post regarding the cable. You will need to ensure that the cable has sufficient slack in the adjustment so it doesn't change idle when you move the bars. Check that the cable isn't catching on something which could pull on it when you turn the bars.
    • Like Like x 1
  5. Thanks GreyBMGreyBM ...

    Plugs have been replaced now and air filter would have been replaced in August (when i got the bike), but I haven't actually checked the condition of the air filter.

    If the bike is running rich, I would like to learn how to adjust the carby mixture myself if its easy enough.

    How do i check the throttle cable to see if theres sufficient slack? I was just looking at the cable from handlebar to where it connects to (throttle adjustment) and seems to have sufficient slack
    It seems to be intermittent though. Idle would drop intermittently when i turn the handlebar to the right.

  6. Just went out to take a look... The bike has cable adjustments at the throttle and looks like two on the carby. With the bars straight you should be able to feel a small amount of slack in the cable, Try turning the bars to the left and to the right and check you still have a small amount o slack. If you don't you will need to adjust the slack. Simply undo the lock nut on the adjuster and wind the gizmo in to create more slack or out to take up slack.

    Don't assume the filter was changed ensure it is in good condition. If it blocked that will be causing/contributing to running rich.

    There is no point trying to play with mixture if other things like air filter are stuffed so sort those out first.

    You adjust mixture by turning the mixture screw on the carby. Before playing, start by looking at the screw and noting roughly where the slot is (e.g. 2 o'clock or 5 o'clock). Then turn the screw all the way in, counting how many turns and part turns that takes. note this down - don't rely on memory. Now if you bugger things up you can wind the screw all the way back in and then back it out by the number of turns you noted. This puts the adjustment back to where you started.

    Once the bike is warmed up (take it for a 15 minute ride)increase the idle just a tad by adjusting the throttle stop then with the engine running slowly turn the mixture screw in until the bike starts to falter. Note the position of the screw and then turn it out until the bike starts to falter again and again note the position of the mixture screw. Generally speaking half way between the falter points will be pretty close to right mixture. Set to that and then reset the throttle stop to adjust the idle to correct revs.

    This is really only affecting the idling mix and if the carb is in bad condition the mix may still be incorrect at revs above idle.

    Whatever you do check the condition of plugs after you have done any adjustments as while running rich is not especially good, running lean for any length of time will cause engine damage.

    I am sure if you search you will find info on this and the owners handbook may even say how many tunrs out the mixture should be, but this assumes everything in good order.
    • Informative Informative x 2
  7. Thanks for your informative post. I will let you know how it goes.

  8. I had one of these bikes and the exact same problem.

    CHOKE CABLE was stretching on full lock, engaging the choke, flooding the engine.

    That's what may be happening to yours.
    • Informative Informative x 1
  9. Yep That would do it too. Check both cables for clearance.

    However choke is pretty much central so would not be as stretched as much as throttle cable when turning the bars,
  10. That plugs totally shagged. Its running way way rich by the looks, or done 100k ::] Think Mick M might be on to something.

    Here are mine after changing at 24k.

    2015-09-29 16.57.07.
  11. Like Mick M I also had this problem on my kid’s bike, the choke cable outer gets hung up under the tank. Once you free it everything should be good.