Need some general info about Suzuki GSX 750

Discussion in 'Motorbike Technical Discussion' started by oldgeezer, Sep 25, 2006.

  1. oldgeezer

    oldgeezer Guest

    Hi,

    Someone (100 miles away) just offered me a GSX750
    built 1984. But before I take a train to where
    he lives, I'd like to have some info about this model.

    II looked in www.bikez.com to find what it
    is, but it is not listed, only the GSX 750 EF is.
    That GSX750 without trailing characters (like ES, EF, F, S, etc)
    seems to be a European model.

    I do not need info such as power and max speed.
    chain drive, air cooled. That will be like I found
    in bikez.com (although it will have less power).

    All I want to know is what the weak points of
    that bike are. Hopefully none...

    Rob.
     
    oldgeezer, Sep 25, 2006
    #1
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  2. oldgeezer

    B-12 Guest

    You probably discovered that it was an air-cooled 16 valve I-4 like the
    GS750ED and ES.

    If you look at the engine numbers, it will say "GSXxxxxxxxxx".

    The weak points of that engine were the starter clutch and the
    permanent magnet alternator.
     
    B-12, Sep 26, 2006
    #2
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  3. And the electronic ignition, electronic tach, and entire charging
    system., including the reg/rec Utterly dreadful electrics.

    Incidentally, we called it the GSX this side of the Pond.
     
    The Older Gentleman, Sep 26, 2006
    #3
  4. oldgeezer

    oldgeezer Guest

    T.O.G and B-12(F.B), thank you.
    This is what I wanted to know.

    The GSX is in pretty good shape, so I think I
    fall for it. But I will pay attention to
    the starter clutch as good as I can.

    It seems Suzuki did not learn much in
    those years. About 30 years ago I owned
    a GT250. It had a severe *basic* problem.
    The rectifier was a full bridge (as it should be)
    but one of the diodes was a thyristor, which
    changed the bridge into a half bridge at around
    13+ Volts, simply shorting the generators at
    the negative parts of the sinuses.
    Thus at full battery, the generators kept on
    pumping amps into the battery, albeit only
    for half the pulses.
    It had two generators, one always in action,
    the second came in when you switched
    on the light.

    When I took a look at the schematics, I
    couldn't believe my eyes. Thought I made
    a mistake.
    But it explained why I sometimes had an
    empty battery. I mean empty, no fluid in it.

    I looked at the schematics after I had a
    momentary short, which blew out the main
    fuse to the battery. This caused both generators
    to cheer: "Hurray, we can now pump out 50 Volts"
    Al my light bulbs were black, only the blinkers
    were intact.

    It made me say: "Never another suzuki":
    But, as it is: Never say never.

    Thanks again, I know enough.
    This thread can be closed.
     
    oldgeezer, Sep 26, 2006
    #4
  5. oldgeezer

    B-12 Guest

    ElectrosportUSA makes improved rectifier regulators with TWO thyristors
    instead of one and they also make a better alternator stator.

    If you buy the GSX, you should check out all the electrical connectors
    in the charging system and eliminate as many connections as possible.
    If one leg of the alternator stator leads up to the headlight shell,
    eliminate that wiring and run that phase direct to the rectifier
    regulator AC insput.

    As for the starter clutch that is bolted to the back of the alternator,
    that was a bad design that Suzuki struggled with. The rotor will try to
    spin off the end of the crank under deceleration.

    Suzuki changed the diameter of the tapered end of the crank for 1984
    GS1100 models, maybe that larger diameter stub was incorporated in the
    1984 GS750 models.

    I cannot tell for sure from looking at the parts diagrams on
    partsfish.com, but it looks like the needle bearing inside the starter
    clutch idler gear was replaced with a
    pressure lubricated bushing.

    I had trouble with the needle bearing on my GT-750. Starter clutches
    that seize up while cruising down the highway at 70 mph can cause the
    motorcycle to slowdown dramatically.
     
    B-12, Sep 26, 2006
    #5
  6. oldgeezer

    oldgeezer Guest

    SoCalTom schreef:

    Wow, more info than I hoped for.
    Thank you all.

    Rob.
     
    oldgeezer, Sep 26, 2006
    #6
  7. Heh. Suzuki Kettle or Kawasaki four?
     
    The Older Gentleman, Sep 26, 2006
    #7
  8. oldgeezer

    Ian Singer Guest

    You say how great B-12 is and how Walmart sells it. Well they don't in
    Canada so do you know who makes it who who might distribute it here? Or
    how does it compare to other brands?

    Ian Singer


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    Ian Singer, Sep 26, 2006
    #8
  9. oldgeezer

    B-12 Guest

    Can you get STP or GumOut carburetor cleaner in an aerosol can? That
    would work just as well, but the advantage of B-12 in the liquid form
    is that you're getting all liquid, no propellant. It's xylene, acetone,
    and methyl alcohol.
     
    B-12, Sep 27, 2006
    #9
  10. oldgeezer

    Ian Singer Guest

    Walmart.ca sells Bardahl No-Smoke Concentrated Fuel System Cleaner which
    is liquid and also Bardahl ALL-U-NEED.

    Canadiantire.ca sells PJ1 Fuel Injector/Carburetor Cleaner and Red Line
    SI-1 Complete Fuel System Cleaner and Prestone Fuel System Cleaner

    Will have to look at ingredients as soon as my "new" tank arrives.

    Ian Singer



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    Ian Singer, Sep 27, 2006
    #10
  11. oldgeezer

    B-12 Guest

    Anything that has "petroleum distillate" in it is better for fuel
    injector *lubrication* than for carburetor cleaning. Stuff called "fuel
    system cleaner" may be intended to absorb condensed water in your gas
    tank and emulsify it with the gasoline so your engine can get rid of it
    by turning it into steam in the combustion chamber.

    Steam in the combustion chamber is not such a bad thing, it removes
    carbon buildup...

    Somebody else on this NG recommended using lacquer thinner for
    carburetor cleaning. You can get that at a paint store.

    Acetone and methyl ethyl ketone can also be bought at a hardware store.


    But, if you've bought a pint of lacquer thinner, a pint of acetone, and
    a pint of MEK to mix together, you've spent at least $15 USD and you
    have enough chemicals to last you for ten years---if it doesn't
    evaporate first.

    That's why Berryman B-12 liquid is the best solution. It's a little
    over $3.00 a pint at Wal*Mart and auto parts chain stores like NAPA
    will usually have it here in the USA.
     
    B-12, Sep 27, 2006
    #11
  12. oldgeezer

    Ian Singer Guest

    Still looking in Canada. NAPA does not carry it but recommends Seafoam
    wich contains Naptha ad IPA.

    Ian Singer


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    Ian Singer, Oct 2, 2006
    #12
  13. oldgeezer

    Ian Singer Guest

    I think I have my gas tank leak fixed with JB weld. Seems OK. I was
    expecting it to dry hard like some of the epoxy putties but it doesn't
    its more like rubber. They say you can also use it extruded, but it must
    take a long time to dry hard enough so build it up into shapes. I was
    going to build a new turn signal knob, but it flops down too easily. I
    didn't get the one that dries in 4 hours but the 24 hr one.

    So when I have has in the tank the carbs drain from the overflow. Are
    you of the opinion that if I could get B12 or something with methanol,
    acetone and xylene and I put that into carbs in 100% solution for 30 min
    it might be able to dissolve the varnish, and not destroy any seals, so
    that the floats will seat and the fuel wont overflow?

    Also found when testing with water that the vacuum operated petcock
    leaks. I have no idea why as the diaphragm has no apparent holes in it.
    If it leaks and the floats seal should be OK.

    The two spare tanks I purchased are both unsuitable as they won't fit
    bike. One with good sensor is no good also as the sensor is
    incompatible with my tank and the petcock on it also leaks. Other tank
    that wont fit has bad sensor and no petcock.


    Ian Singer

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    Ian Singer, Oct 17, 2006
    #13
  14. oldgeezer

    B-12 Guest

    Every time I've used JB Weld, the result was a reasonably hard dark
    grey glob that
    stuck to the degreased and roughened metal. It won't survive a great
    deal of mechanical stress, but if it's applied over a large enough
    area, it sticks to the metal.

    The JB Wels that I have used has two parts. One part is yellowish white
    and the other part is very dark grey, verging on black. Mixed in equal
    proportions and cured at about 75 or 80 degrees F for 15 hours, it
    isn't gummy at all.
    That's what I have done with my carbs when they get really plugged up.
    The acetone will begin to attack some softer plastics after half an
    hour or so, but pump gasoline does come blended with alcohols that are
    intended to keep the passages clean, so internal plastic parts have to
    be resistant to those solvents.
    The rubber parts in a petcock will get hard and leak if the tank is
    stored empty for a long time. The petcock may leak until the gasoline
    softens the rubber parts.
     
    B-12, Oct 17, 2006
    #14
  15. oldgeezer

    Ian Singer Guest

    B-12:

    There is a chain in Canada called Partsource that has a private brand of
    Revive. They sell a carb cleaner by the gallon that sounds similar to
    B-12 in that it has xylene and methanol in it but its designed to be
    used as a bath. They suggest mixing in the gas tank wight be dangerous
    due to its flammability but they dont know

    If B-12 is not available here do you think in your personal opinion that
    it would be save to use, say a 1:1 mix, in the gas tank or if the carbs
    were removed, which I am trying to get away from, could they just be
    filled and soaked but not disassembled??

    If disassembly is required then they probably need all new gaskets and
    seals and re-balancing with vacuum gage.

    At the moment the engine will only run on one cylinder though.
    Waiting for replacement petcock and then might try new plugs first.

    Ian Singer



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    Ian Singer, Oct 29, 2006
    #15
  16. oldgeezer

    B-12 Guest

    Well, Indy cars run on methanol, and I have even seen an 108 octane
    methanol gas pump
    at a neighborhood gas station. You've probably noticed that the pit
    crew at Indy car races squirt the filler nozzle with water to dilute
    the methanol and they fight methanol fires with water because water
    won't spread the fire, but rather cools everything down, so methanol is
    considered a safer fuel than gasoline.

    But the Indy cars carry 40 gallons of it, and I'm only recommending
    putting 4 ounces of B-12 into a full tank of gasoline, so how dangerous
    is that?

    Racers who liked to experiment around with exotic fuel mixes run as
    much as 75% methane with various
    other things, like acetone and benzene.

    But they are aware that the methanol and other solvents will eventually
    eat up the rubber and plastic parts in their carburetors, so they keep
    new spare parts handy.
    That's what I do to avoid a complete disassembly. I mix B-12 with
    gasoline 50/50 and leave it in the carbs for half an hour and start the
    engine on the B-12/gasoline mixture and burn it out.
    You can order aftermarket carburetor rebuild kits from
    www.oldbikebarn.com for about $20 to $25 USD per kit. The kits do not
    include the rubber diaphragms, so if one is torn you'll want to order a
    new one from those guys in England.
    Well, if you have spark and gasoline and compression, the engine has to
    run, doesn't it?

    Since motorcycles began to be equipped with electronic ignitions in the
    1980's, dirty carburetors have emerged as the leading problem in the
    "my motorcycle won't start" syndrome.

    The other possibility is intake or exhaust valves that don't seat and
    allow compression to build up.
     
    B-12, Oct 29, 2006
    #16
  17. oldgeezer

    Ian Singer Guest

    I was trying to start with 4oz of Wnnys carb cleraner in 1/2 gallon gas
    and using starter ether. I am just assuming, and hoping super gummed up
    Suppose I should try and drain the Wynns tahts been in carb for a week
    but those drain bolts are hard to get to.
    With my luck NO
    Well if I really cant start it will have to get a compression tester. I
    its bad I try the spare engine!

    Ian Singer


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    Ian Singer, Oct 29, 2006
    #17
  18. oldgeezer

    B-12 Guest

    That sounds like something the Saudis would do. They had very little
    (if any) understanding of the internal mechanisms of machinery.

    If the fan belt broke, they would install a whole new engine in the
    truck, using the new tools and following the manuals my company
    provided.

    Their theory was, if the engine *looked* new, it must be OK.

    If you're going to mess around with old crocks, you're going to have to
    learn to wrench on them. You'll figure out what is worth your time and
    what isn't. I wouldn't go through an engine change if I could fix the
    original engine by cleaning the carburetors.

    OTOH, I wouldn't bother to split the cases and do a lower end or
    internal transmission repair on a 25 to 30 year old motorbike, it's
    just not worth my time. I can buy a new one for $10 to $15 USD a week,
    why bust my knuckles on a POS?

    Maybe you do have a compression problem. I broke my compression tester
    and didn't have one
    to help me troubleshoot a problem which I finally concluded was due to
    low compression.

    So I fabricated a pressurization tester out of a tire pump and an old
    spark plug. I pumped furiously, and couldn't build up any pressure on
    two adjacent cylinders.

    The head gasket had blown between adjacent cylinders. One piston was
    actually forcing the fresh intake charge right back out the intake
    valve because the adjacent pistons were moving in opposite directions.

    So I decided to do a valve job, and do it right. Cost me $400 USD to
    fix a vehicle that was worth $1000 USD. By the time I put new tires and
    brakes and fixed the ball joints, I'd spent $1400 on it and it still
    needed paint and upholstery...
     
    B-12, Oct 29, 2006
    #18
  19. oldgeezer

    Ian Singer Guest

    For those interested in the contents and handling precautions for B-12
    see http://msds.ogden.disa.mil/msds/owa/web_msds.display?imsdsnr=193984

    Ian Singer

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    Ian Singer, Oct 30, 2006
    #19
  20. oldgeezer

    B-12 Guest

    FWIW:

    If you want to learn about the contents and handling precautions of
    unleaded gasoline, you can probably find the Material Safety Data Sheet
    on that stuff, too.

    If you're like many of us, you keep about ten gallons of unleaded
    gasoline in the tank of your car (or the tanks of your motorcycles) at
    all times, and you park your vehicles in the garage that's attached to
    your house, and you never think twice about doing that.
     
    B-12, Oct 30, 2006
    #20
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