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Help 250 Katana starting issue

Discussion in 'Your 250cc Projects' started by MotorGirl, Apr 13, 2022.

  1. MotorGirl

    MotorGirl Active Member

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    Hi all.
    Been working on my GSX250S Katana and it developed a starting issue recently. So first start after sitting overnight it fires first time and runs fine...all cylinders working and sounds great. When I go to restart...it just runs the starter and no firing...a few days ago after this I pulled plug 4 to find it wet. The plugs are new as of a week ago. Today I fitted new coils as it seemed like the coil secondary resistance was low...I don't have a workshop manual as they are in Japanese so it's a bit tricky trying to resolve this.
    What I have done to date:
    Checked all electrical connectors including cleaning and replacing rear lights.
    New spark plugs
    Checked the tank and fuel flow including cleaning petcock.
    Starter seems fine
    Battery holds charge etc
    When it goes - it rides really well with no bogging or dead spots and throttles well.
    I'm stumped as the coils are now new and still not firing the second time around.
    Any ideas on what might be causing this?
    Thanks
     
    MotorGirl, Apr 13, 2022
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  2. jmw76

    jmw76 Well-Known Member

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    Hi MotorGirl, that is a bit puzzling.

    Unfortunately this little engines can be a little finicky at times.
    Can you check that all the plugs are ok. This can be done quickly while they are in the bike.
    Take off the plug caps and using a multimeter, measure the resistance between the terminal on each plug and the cylinder head/ground. You should not observe any resistance when you have your meter set to its highest megohm range. If you see anything, suspect that that plug is not likely to fire.

    Also have you confirmed that you have spark at each plug lead. Only remove one lead at a time when checking for a spark to the cylinder head/ground.

    With the plugs being wet, you obviously have fuel. You might have too much, which could be contributing to your problems.
    Pulling the carbs off the bike and giving them a total refurb/clean often solves many of these issues. Refer to some of the other threads on this forum.

    Good luck.

    Report back with your findings.

    Peter.
     
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    jmw76, Apr 13, 2022
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  3. MotorGirl

    MotorGirl Active Member

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    Thanks Peter
    I just put new spec plugs in and had weak spark which is why I thought it was the coils...e.g. not enough spark...Will check carbs next week and see how I go.
    Cheers mate
     
    MotorGirl, Apr 13, 2022
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  4. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    What is the battery voltage when under load ie trying to start the bike. It may hold charge but be weak.

    I've no experience with the 250 Katanas but they can't be all that different from similar Suzuki's of the era.

    About the wet plugs. Are they black and sooty? Or just wet? Are they wet with fuel or with oil, or both?
     
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    Linkin, Apr 13, 2022
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  5. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Describe your starting procedure please in both cases, hot and cold.
    Coils are never the problem.
     
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    maelstrom, Apr 13, 2022
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  6. jmw76

    jmw76 Well-Known Member

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    @MotorGirl I understand that you put new plugs in, but trust me it is worth doing the simple resistance test.
    I have had situations where new plugs have gone bad within a very short time. I tried cleaning them to no avail and ended up replacing them again. At least if the resistance checks out, you can then rule out the plugs as the issue.

    Peter.
     
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    jmw76, Apr 14, 2022
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  7. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    GreyImport, Apr 14, 2022
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  8. MotorGirl

    MotorGirl Active Member

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    Hi all.
    It's been a busy few weeks. Following up your suggestions for the starting issue on my Kat.
    I checked the battery under load and it puts out 13+ volts and holds charge.
    I rechecked all the electrical connectors and earths across the whole bike.
    Coil resistance is good (coils are new).
    Checked spark on all plugs - seems good - regapped the plugs to be sure...no carbonisation on plugs
    When the bike runs it is perfect- all 4 running well, no bogging or flat spots, sounds clean and no smoke ...
    I actually bought a new CDI unit - as this seemed to be the only likely culprit left to try ( well really could be anything but this was the only thing left to check).
    Have left well enough alone with the carbies - at this stage as it's running beautifully once started.
    Bike is now starting better although not perfect...
    I have got it through road worthy and putting on historic / club rego - this should be by the end of the week.
    Going to ride around for a few weeks to see if it settles...
    Carbies will be stripped and rebuilt in a few weeks...
    Thanks all for your invaluable suggestions.

    20220405_104712.jpg
     
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    MotorGirl, May 11, 2022
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