93 katana 750 headache, please help

Discussion in 'Motorbike Technical Discussion' started by jrcouture, Apr 22, 2007.

  1. jrcouture

    jrcouture Guest

    Bought it a few weeks ago, it ran, not well but it did.

    Apparently it was originally a 600cc and was swapped for a 750.

    Pulled plugs, replaced them - tested each against the engine bloc,
    each sparked.

    Pulled the carbs off. cleaned all the linkage, removed the float
    needle and the jet. one was clogged, cleaned it out, replaced them

    Starter turns it over, and over, and over, and over - but ... nothing

    I had been able to get it to run by spraying some carb cleaner in the
    carbs while starting it - but even then it would only barely run with
    the throttle wide open. it struggles, but it sounds like it wants to

    also, i had a hunch that it might only be firing on one or two
    cylinders? this katana has two ignition coils that control alternate
    cylinders, presumably one controlling the idle, and the other
    controlling... i don't know - does any of this make sense?

    what is my next step?

    i can't afford hourly shop rates, please help.

    jrcouture, Apr 22, 2007
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  2. jrcouture

    Ian Singer Guest

    I can't speak for your engine but on a GS650 the left plug (when sitting
    on bike) fires cylinders 1 and 4, and the right one fires cylinders 2 and 3.

    Ian Singer


    See my homepage at http://www.iansinger.com
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    I am near Toronto Canada, can I tell where you are from your reply?
    Ian Singer, Apr 22, 2007
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  3. jrcouture

    Albrecht Guest

    That's not impossible, since Suzuki designed the GSXR and the Katana
    series with modular intent, i.e., a GSXR1100 or an 1100 Katana
    crankcase would fit into a GSXR600 or Katana 600 frame. But the
    largest engine would have taller cylinders and you might have to cut
    the valve cover in half to install it. Swapping a GSXR750 or a Katana
    750 motor into a Katana 600 frame is simpler.
    You need to find the idle mixture screws, remove them, and clean out
    all the idle mixture passages. Look underneath the installed
    carburetors with a mirror. The idle mixture screws will be forward of
    the float bowls. If you see a round plug, you will have to carefully
    drill the plugs out, as has been described here many, many, many

    Google up "EPA anti-tamper plugs".
    If the idle speed knob is turn too far clockwise, the starting
    enrichener is defeated by low vacuum downstream of the throttle
    Your Katana doesn't have a choke, it has a little valve built into the
    side of each carburetor. When you move the "choke" to the full ON
    position, you aren't "choking" the engine, you're opening an air
    bypass around the throttle butterfly. Air going through the bypass
    sucks gasoline directly out of the float bowls through a brass tube,
    like a kid drinking milk through a straw. if the master idle knob is
    turned too far clockwise, vacuum is too low to suck gasoline through
    the brass tube.
    Open the float bowl drain screws, and drain the float bowls into an
    old rag. Then disconnect the fuel line from the petcock and fill the
    carburetors with a mixture of 50% gasoline/50% carburetor cleaner.

    Leave that stuff in the carbs for half an hour and then start the
    engine with the master idle knob turned as far counterclockwise as it
    takes to completely close the throttle butterflies.

    Don't turn the throttle twist grip until the engine fires up on full
    "choke". Then you can keep the engine running by holding the throttle
    open until the engine warms up. When it'swarm, you can readjust the
    master idle knob.

    Pour four or five ounces of carburetor cleaner into a full tank of
    gasoline and go for a slow ride to clean the idle jets out. You may
    have to stop and turn the idle speed down. That's good, it means that
    the idle jets are getting cleaned out.
    It's firing a little on the cylinders with the cleanest carburetors.
    No. Japanese four cylinder motorcycles have been built with two twin
    lead coils for almost 40 years now. The coil on the left side should
    be hooked to the cylinder on the #1 cylinder on the left side and the
    #4 cylinder on the right side. The leads from the coil on the right
    side should be hooked to the #2 and #3 cylinders, which are in the
    Hook your coils up correctly. Clean your carbs out.
    Niether can I. That's why I learned how to clean and adjust my own

    If you want to know all about carburetors like you have on your
    Katana, just google for messages from this group about "CV
    Albrecht, Apr 22, 2007
  4. jrcouture

    John Johnson Guest

    Did you replace all the jets in the carb, and did you verify that all
    jets and passageways are clear of junk? That you can start it only by
    spraying an accelerant makes me think that your pilot jets are plugged
    up still.

    If you haven't already, look up Krusty kritter's carb cleaning
    insctructions (posted to this group many times in the past, look in the
    archives via google, etc.). They're pretty thorough.


    'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.
    John Johnson, Apr 22, 2007
  5. jrcouture

    FOG Guest

    I assume that you have checked the fuel taps for flow? clogged fuel filter
    in the tap?
    FOG, Apr 23, 2007
  6. jrcouture

    jrcouture Guest

    I cleaned (to the best of my knowledge) the carburettors. I pulled the
    float needles and the jets out, cleaned and freed them.

    While cleaning them, what I believe to be the Slow Jet (#8, according
    to the CV Carburetor Cutaway @ http://www.nightrider.com/biketech/hd_cv_mods.htm
    ) was stuck inside the threads of the 3rd carb. I might have stripped
    the flat screwdriver slot, in which case I'll need to tap it.

    Cleaned the tank, the petcock and the carb linkage.

    The starter just clicks over and over. I checked the spark plugs,
    which seem to have spark against the engine block, but three of them
    often come out looking oily and damp, suggesting bad valve seals?

    Any help would be...helpful.
    jrcouture, Apr 24, 2007
  7. jrcouture

    Albrecht Guest

    Did you drill out the EPA plugs so you could take the idle mixture
    screws (# 9 on the cutaway) out and squirt carb cleaner through all
    the ports and passages?

    You'll need to do that, and you'll need to find the pilot air jet
    (it's either in the carburetor intake or under the rubber diapraghm)
    and squirt carb cleaner through that hole too, as the passage connects
    to the slow jet and to the transistion ports down stream of the
    throttle plate.
    I would suggest just leaving the buggered jet alone and squirting carb
    cleaner through it until it flows freely out of the transition ports
    and the idle port downstream of the throttle plate.

    The slow jet is also called the "idle jet" or the "pilot jet". It
    controls the flow of gasoline to the idle mixture screw and the three
    transition ports downstream of the throttle plate.

    The slow jet is cross drilled so air can immediately mix with gasoline
    from the float bowl and go on to the idle mixture circuit that feeds
    the engine during part throttle operations.

    Did you have to remove a small rubber plug to see the end of the "slow
    jet"? The correct carburetors for the GSX750P Katana have rubber plugs
    and the slow jet has to suck gasoline through the main jet through a
    diagonally drilled passage. The plug is #35 on the
    schematic at www.bikebandit.com

    Click on OEM parts > Suzuki > 1993 > GSX750P > carburetor to see the
    correct carburtors.
    Your battery is too weak to hold the starter solenoid contacts closed
    when the voltage drops from trying to crank the engine over.
    Maybe. They also may be wet from gasoline. Clean the oiliness off with
    fresh gasoline, sandpaper all the carbon off the insulator nose with
    fine grit sandpaper or replace the plugs with new ones.
    If you really have a 600cc Katana with a 750 motor in it, check the
    frame numbers.


    1993 Katana 750
    Starting frame number: GR78A-125061

    1993 GSX600FP (frame numbers GN72A-118194 to GN72A-121464)
    Albrecht, Apr 24, 2007
  8. jrcouture

    Albrecht Guest

    You have to clean out the tiny air passages and fuel passages in the
    carburetor body. Just cleaning the jets won't clean the passages.
    Google this group for "passages" and "ports" and you'll learn how to
    clean them.
    You should probably just leave it alone.
    Weak battery.

    I checked the spark plugs,
    Maybe. It could just be gasoline fouling from the old gas in your tank
    and the fact that your engine didn't start after several attempts.

    Clean or replace th spark plugs after you do a proper job of cleaning
    the carbs and replacing the old battery.
    Albrecht, Apr 24, 2007
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