GPZ600R Enginer & Handling Issues - Any Suggestions?

Discussion in 'Motorbike Technical Discussion' started by Rabbit, Aug 14, 2010.

  1. Rabbit

    Rabbit Guest

    Hi. I've been having a couple of issues with my 1985 GPZ600R recently.

    Firstly, occasionally the engine does a wierd thing. After starting
    the bike (which goes as planned) the engine will run as normal. Then
    shortly afterwards it may bog down and won't rev past about 3k rpm, no
    matter how much you twist the throttle or play with the choke. It runs
    like this for quite a while and then seems to clear itself (it also
    fixes itself if you leave it off for a few minutes). When it does
    clear out it gives some smoke out the back as it revs, then it will
    run fine for a long time. I have checked the spark plugs (new set in
    now) which were quite sooted up. I believe she is running quite rich
    at the moment. Does anyone have any ideas what might be causing this?
    The next step I'm taking is to replace the air filter and then re-tune
    the carbs to be leaner.

    Secondly, I am having an issue with the handling of the bike. I'm not
    sure how best to describe it. If your travelling along in a straight
    line at about 70mph the problem is noticeable. It feels almost like
    the rear is moving slightly from side to side (or it could be an issue
    from the front). It's like it's trying to track in a straight line but
    doesn't. It doesn't seem to oscillate and get out of hand. I think it
    occurs at all speeds and when cornering but it is definitely worse the
    faster you go. I have recently replaced the swingarm bearings, shock
    lingage bushes, rear bearings (including sprocket), chain and both
    sprockets. I have a fairly recent pair of BT45s on and the tyre
    pressures are correct. I am at a loss for what could be causing this,
    I was thinking it might be an alignment issue somewhere or maybe the
    shock and forks are shot. Does anyone have any suggestions? I don't
    really enjoy riding the bike at the moment.


    Rabbit, Aug 14, 2010
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  2. The fuel system may be dirty, all the way from the fuel tank into the
    float bowls and into the idle mixture system.

    When the idle jets and idle ports really gets plugged up with gum and
    varnish and little bits of rust from inside the gas tank, the engine
    will not respond to the throttle but will still run on the "choke".

    The "choke" is not actally a plate type choke at all, it's an air
    bypass passage built into the side of each carburetter. When the
    "choke" lever is moved, a small air valve is opened and fuel is sucked
    up from the float bowls through a small brass tube.
    Well, actually, the "choke" system will supply an air/fuel mixture of
    about 1:2 or 1:3 in dorder to start the engine, as compared to a 1:14
    mixture for cruising operation, so the indications you'll see on the
    spark plugs give the correct impression that "she is running quite

    But if you're running the engine on the choke to avoid fixing a dirty
    fuel system problem, whose fault is that?
    See above.
    No, clean out the fuel system first. You can drain most of the
    gasoline out of the gas tank and remove the two little screws holding
    the fuel selector lever onto the
    automatic fuel petcock.

    If there is a bunch of rust particles in any of the four fuel ports
    you see facing you, you should remove the petcock completely and clean
    the fuel filter screen and flush out the fuel tank.

    Also, be sure to check that the small vacuum hose on the backside of
    the fuel petcock doesn't have a split end, causing a vacuum leak and
    intermittent fuel supply.

    If the fuel tank doesn't appear to have water, rust and other debris
    in it, you can try cleaning out the carburetors without dismantling
    them by adding about 4 ounces of CLEAR carburetor cleaner to a fuel
    tank of gas and riding until the engine begins to run better.

    It's a good idea to know where the master idle adjustment knob on the
    carburetors is located before you set out on a ride with carburetor
    cleaner in the gas tank, because you will need to turn the idle RPM
    down at some point.
    A motorcycle is ALWAYS trying to fall over to one side or the other,
    and the front steering geometry is ALWAYS trying to push it back

    To the observant rider, it feels like the motorcycle is rocking
    slightly from side to side.
    Well, save your money until you figure out what motorcycle do

    You'll waste a lot of hard-earned ca$h chasing imaginary handling
    BT45's are a dual tread compound tire. I have a set on my old GSXR-750
    and I don't like them.

    You might just be feeling the difference between the center compound
    and the side compound as the motorcycle normally rocks a little from
    side to side.

    This rocking is exaggerated with 16-inch wheels...
    schwarzesonne, Aug 14, 2010
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  3. Rabbit

    S'mee Guest

    On Aug 14, 4:18 pm, schwarzesonne <>

    Oh piss off you pervert...Thanks to reading what you cut and paste
    you've finally learned to relay it by rote. As for the BT45's they are
    fine and how would you know? You do not own the motorcycle you claim
    to own and for that matter you've never ridden a motorcycle in you
    geritric lying life.
    S'mee, Aug 15, 2010
  4. Rabbit

    S'mee Guest

    Drain the fuel tank and refill with fresh CLEAN fuel. That means put
    it on reserve and let it sit...tilt it to the side where the petcock
    is. Then put in a quality fuel system cleaner. In the states the
    prefered stuff is called SEAFOAM, not sure what is available where you
    live but whatever the guys at a marina use can't hurt.

    If that doesn't help you will either end up rebuilding the carbs or
    having it done.

    As for handling I'd check ALL the bushing the headstock bearing etc
    for excessive wear. There are some good tutorials on the web for
    checking these things. Unless your tyres are worn it isn't the matter what that fraud 'schwarzesonne' aka krusty kritter
    says, he is an unskilled fraud that parrots what he reads and usually
    gets compleately wrong.
    S'mee, Aug 15, 2010
  5. SeaFoam is just about worthless for cleaning out motorcycle fuel
    systems because it's just a light, straw-colored oil to free up seized
    pistons from rusty cylinders and isopropyl alcohol that will absorb

    The hot mix for cleaning motorcycle fuel systems in the USA is
    Berryman B-12 Choke and Carburetor Cleaner which is a powerful mixture
    of methyl alcohol, toulene, xylene, and acetone which will cut right
    through gum and varnish.

    B-12 comes in liquid form and in an aerosol can for about $3.50 a
    You can spent hours and hours looking for mechanical problems and
    discover in the end it's just a matter of suspension setting and tire
    pressure *adjustment*.
    schwarzesonne, Aug 15, 2010
  6. Absolute nonsense. And why have you morphed again?
    The Older Gentleman, Aug 15, 2010
  7. Yes, it's running rich. Gunged up carbs: very common. Has the bike been
    standing for long? I suspect so. You could try carb cleaner but if
    they're reall bad, ulrasound cleaning is the best way.
    Check everything again. Check also the head races. Check you've actually
    got the right size tyres fitted. Check the swingarm pivot hasn't been
    under-rightened so is loose. The 600R has 16" wheels fore and aft and
    does feel twitchy as stock.
    The Older Gentleman, Aug 15, 2010
  8. Rabbit

    mred Guest

    Hi I have been riding bikes since I was 15 and am 76 now .
    so I have a little experience.

    I use Lucas fuel conditioner in my bike with each tankful of gas This
    helps to keep the grunge out of the carbs and fuel lines as well as
    any condensation in the tank.

    I use the same Lucas fuel additive in my 2002 Camry -4 and havent ever
    had a problem in either vehicle

    For winter storage I fill up with FRESH gas and then add the Lucas and

    And the bike is stored for almost 6 months here in Ontario Canada.
    NEVER had a problem with spring start-up .except once when the battery
    died , a new battery fixed that problem.


    Condensate will encourage the formation of gas line sludge , blocking
    the fuel filter and possibly the gas lines.

    Something else I have been doing when I go out for a ride is lubricate
    the chain each time (2001 750 Shadow)

    I also run the bike on RESERVE for several miles to make sure THAT
    line isnt plugged and I have free gas flow when I need it.

    Sounds to me that your fuel filter may be partially blocked and as
    suggested on here a GOOD carb cleaner might help.

    If you follow the procedure like I mentioned afterward ? when the bike
    is running good you will NEVER have another fuel related problem

    I have ridden everything from an Excelsiour two stroke CB 500
    Honda ,to Intruder 1400, Goldwings and Venture Royales .

    A bad back keeps me to the 750 Shadow now.
    good luck
    mred, Aug 15, 2010
  9. Might not hurt to also check the swingarm and maybe the
    wheel bearings and just for laughs, dump the whole tank
    of gas into your car's tank and refill the bike with new. I
    usually figure any fuel problem will get well diluted in the
    car's tank, especially if I top off afterward.
    Rob Kleinschmidt, Aug 15, 2010
  10. Rabbit

    S'mee Guest

    Yeah right this coming from you? HAHAAHAHAHAH you fucking liar. The
    difference betwee you adn I is that I DO things and tell people how
    they worked and you just talk out your ignorant stupid eneducated ass.
    Reading the web page again I see.
    In you infinate stupidity you ASSUME he lives in the states.
    No you'd be wrong as **** yet again.
    S'mee, Aug 15, 2010
  11. schwarzesonne, Aug 15, 2010
  12. Nope. I was replying to YOUR assinine assertion that SeaFoam was a
    good carb cleaner.

    And I know *exactly* where to find ewe, goatse...
    schwarzesonne, Aug 15, 2010
  13. Rabbit

    Rabbit Guest

    Firstly, thank you for all the replies. Hopefully these issues can be
    I'm not running the bike on choke, I just said it didn't make a
    difference. I think it's just being tempermetal when it hasn't run for
    a while, but it's a relatively new issue. Maybe I'm not running it as
    often as I used to.
    I think I'll give this a go as it will certainly do the bike some
    good. I have cleaned out the carbs before but I haven't done anything
    to the tank, filter or fuel hoses.
    I'll give that a go before taking the carbs apart again. It's not so
    much hastle taking carbs apart, just getting they in/out og the bike
    due to the rubber etc. It's a biatch.
    I am aware of this and it is not the problem. My bike used to be fine,
    it was fine up to about 100mph (rarely take it faster) with no issues.
    The issue I have is not just normal bike riding.
    This can't be the case because it occurs when riding in a straight
    line as well as learnt over.
    I am familiar with the bike when it was working better. True, it could
    be caused by my recent change in tyres but it certainly doesn't feel
    Again, this has been done (although not recently, and it has sat for a
    little while).
    During this summer I've done the front wheel bearings, rear wheel
    bearings (inc sprocket), swingarm bearing and the linkage bushes. I
    haven't replaced the cushdrive but it looks alright. I had a friend
    have a quick look at the headstock bearing whilst I pushed down on the
    seat and he said it was fine, but then I might go have a look for
    myself (as it sounds like that might be the issue).
    I will be taking the bike to a garage soon to check that all the bolts
    etc that were done up when the bearings/bushes were done are done up
    to the correct torque. I'm not an expert but there doesn't seem to be
    any play in the rear end.
    See above.

    Basicaly I'll take a look at the fuel system and the bearings and see
    what I can do. I have been planning to sort out the shock and forks at
    some point soon as they are probably knackered by now. Do you think a
    knackered shock could effect the handling in this way.

    Thanks again for the wisdom. I'll let you know how I get on.

    Rabbit, Aug 15, 2010
  14. Rabbit

    Rabbit Guest

    Oh yeah, by the way I'm in the UK, not US. But cheers for giving names
    of the products, we can get a lot of similar stuff over here.
    Rabbit, Aug 15, 2010
  15. Trans: Because I'm trying to set up a new ID so that newbies won't see
    my past record.

    OK, what do you know about GPZ600Rs? I rode my first in 1985 and have
    had a lot of fun on them since then. You've almost certainly never
    ridden one at all.
    The Older Gentleman, Aug 15, 2010
  16. There was a Buyers' Guide to GPZ600Rs printed in a recent issue of
    Practical Sportsbikes in the UK. Might be worth getting a copy.

    It'll be more value than Krusty's pronouncements.
    The Older Gentleman, Aug 15, 2010
  17. Indeed. What you quoted was utter crap.
    As was the quoted text here.
    The Older Gentleman, Aug 15, 2010
  18. <shuffles feet>

    I thought I was the only cheapskate to do this....
    The Older Gentleman, Aug 15, 2010
  19. <shuffles feet again>

    (bloody shoe soles are wearing out in this thread)
    The Older Gentleman, Aug 15, 2010
  20. Use it to light a BBQ?

    No, I made that mistake once, and a whole gallon of fuel ignited. Big
    mistake. BIG.
    The Older Gentleman, Aug 15, 2010
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