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  1. #1
    Where Am I ?
    My Bike(s)
    '87 Yamaha FZ700
    Location
    Milwaukee, WI
    Posts
    26

    FUEL PROB???NEED HELP!!! FZ-700 starves/runs hot

    I just bought a Yamaha FZ700. At a steady 4000rpm or more the bike seems like its running out of gas. It will run fine for about 30 seconds then the problem occurs (sputters and . All I have to do is pull in the clutch for 2 seconds and its fine for 30 more seconds (give or take). I looked at the spark plugs and they are white as a ghost on the tips (running hot). The guy who owned it b4 me has tried a couple different things. He increased the jet sizes. He put in a new fuel pump. He cleaned the carbs. None of these made any difference at all. Any reccomendations would be highly appreciated. THANX

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  3. #2
    M-J Lifetime Achievement Award
    My Bike(s)
    '10 Kaw Vulcan 900 Custom
    Location
    Ocala, FL
    Posts
    8,277
    Fuel filter
    Vacume leak
    Timing advance not working
    Float(s) set too low
    Restricted air cleaner or exhaust (but that would tend to make it run rich)

    If it is only the very tip of the insulator that is white (ie very clean), that is not necessarily a bad thing.
    Don't believe everything that you think.

  4. #3
    Seat Tester
    My Bike(s)
    BMW R 1100 RSL
    Location
    Colorado
    Posts
    77
    check the tank vent as well.
    It may be pinched, causing the tank to pull a vacuum.
    But not really too likely if it only takes 30 seconds to re appear.
    float levels may be the most likely.

  5. #4
    Wants Better Weather
    My Bike(s)
    M-50
    Posts
    682
    My vote is the float

  6. #5
    Just Won't Go Away !
    My Bike(s)
    2010 Hayabusa... a black one... the fastest colour
    Location
    Perth WA
    Posts
    4,934
    Also the float needles may be sticking or debris is clogging them. Try the fuel filters too and all fuel lines. Is this model a vacuum operated fuel tap...if so... and it is almost certain... are you getting a decent vacuum to it and how is the pipe?

    From your description the bike is running very lean and under load there is insufficient fuel, as it takes 30 seconds or so to happen it has to be fuel delivery.
    Last edited by Aussie Steve; 06-04-2007 at 06:31 PM. Reason: Sp
    Smoke me a kipper I'll be home in time for breakfast

  7. #6
    Where Am I ?
    My Bike(s)
    '87 Yamaha FZ700
    Location
    Milwaukee, WI
    Posts
    26
    [QUOTE=Aussie Steve;319769]are you getting a decent vacuum to it and how is the pipe?QUOTE]
    If I open my tank when the problem occurs and the problem still happens does that rule out vacuum problems? Also I drained the tank yesterday through the petcock and fuel flow was unrestricted so I'm assuming the tank in vented properly, but I will check to make sure.
    On my inline fuel filter the gas just sits at the bottom not even filling it 1/3 of the way(air in the rest). When I hit the throttle it trickles in a little faster, but never fills with gas unless I disconnect it from the carb then it fills up all the way and drains(this may be normal I really don't know a lot about bikes yet. .

  8. #7
    Seat Tester
    My Bike(s)
    BMW R 1100 RSL
    Location
    Colorado
    Posts
    77
    Taking the cap off the gas tank eleminates tank venting problems, but not vacuum problems.

    If the filter comming out of the tank doesn't fill, and seems to run slow, seems to me the fuel outlet from the tank is probable clooged. Most likely rust.
    Drain the tank, and take the fuel petcock out and check for clogging and clean it. Also check the inside of the tank for rust. You may have to "Kream" the inside of the tank to stop this.

    eBay: Kreem Motorcycle Gas Tank Prep and Treatment 3 Bottles (item 180122799636 end time Jun-09-07 18:15:00 PDT)

  9. #8
    M-J Lifetime Achievement Award
    My Bike(s)
    '10 Kaw Vulcan 900 Custom
    Location
    Ocala, FL
    Posts
    8,277
    Quote Originally Posted by karlfitt View Post
    If the filter comming out of the tank doesn't fill, and seems to run slow, seems to me the fuel outlet from the tank is probable clooged. Most likely rust.
    Well, I think he said he already tested the fuel flow and it's good.....maybe not through the in-line filter though.

    It is common to have that air bubble in the filter; that should not be a problem. Filters are cheap so if there is any question about it, I'd change it out.

    A little bit of rust inside the tank is NOT something to panic about. If it isn't bad enough to clog the screens or the inline filter, then it's not a problem.
    Don't believe everything that you think.

  10. #9
    Where Am I ?
    My Bike(s)
    '87 Yamaha FZ700
    Location
    Milwaukee, WI
    Posts
    26
    Ok I have done a little more eliminating of what its not. The petcock flows without restriction, the line is not stuck or kinked. The tank is not rusted at all I took out the universal fuel pump the previous owner installed and put in the original. I thought I had the problem solved. It ran fine for 2-3 miles at 4000-6000 rpm's(first time ever). Then on my way home I rode a little harder than ussual to be sure it was fixed and it happened again. Not nearly as bad as b4 though. Then it started to rain so I couldn't really lay on the throttle again so I will retest later. Thanks for all the help!
    Last edited by nuckles25; 06-05-2007 at 02:00 PM. Reason: no rust in tank

  11. #10
    Where Am I ?
    My Bike(s)
    '87 Yamaha FZ700
    Location
    Milwaukee, WI
    Posts
    26
    I took it back out and it ran great no trouble at all. Except it started to shake at about 90mph(6000rpm). Is there anything I can do about that? I would really like to see what more this bike has to offer in the next 5000 rpms, what can I expect for $650 bux. It has brand new rubber, it was in an accident up front and thats where the shaking seems to be from. I will check for lose bolts and bent rim/forks but other than that I am clueless.

  12. #11
    Seat Tester
    My Bike(s)
    BMW R 1100 RSL
    Location
    Colorado
    Posts
    77
    If it was hit up front, yes check VERY close to see if anything is bent.

    Check balance on both tires.

    After you check the front end, and have the front rebalanced, make sure there is no binding in the front foek.
    Here is a good procedure for that.

    put the front tire on, do not tighten the front axle all the way.
    If you have a fork brace, loosen it.

    loosen the top triple clamp, the only thing tight now should be the lower triple clamp.

    Grab the front brake (so the bike doesn't roll) and cycle the front suspension a few times. Now tighten the front axle.

    Grab the front brake again and cycle the front suspension again. Now tighten the top triple clamp.

    Check the fork brace, does it fit perectly in it's mounts? Or will tightening the bolts put a stress on it?
    Make it fit without any stress, use shims to fill gaps. Or you can file a high spot on the mount. But get it to fit perfect.

    Then cycle the suspension one more time and tighten the fork brace.

  13. #12
    M-J Lifetime Achievement Award
    My Bike(s)
    '10 Kaw Vulcan 900 Custom
    Location
    Ocala, FL
    Posts
    8,277
    Quote Originally Posted by nuckles25 View Post
    I took it back out and it ran great no trouble at all. Except it started to shake at about 90mph(6000rpm). Is there anything I can do about that? I would really like to see what more this bike has to offer in the next 5000 rpms,
    Let me get this straight. You have a bike that has been wrecked AND you want to run it faster than 90 mph..... even though it has head shake at that speed? Do you have a death wish??? What it "has to offer" above 90 is a probable trip to the ER.......or the morgue.
    Don't believe everything that you think.

  14. #13
    Where Am I ?
    My Bike(s)
    '87 Yamaha FZ700
    Location
    Milwaukee, WI
    Posts
    26

    Exclamation

    Quote Originally Posted by Easy Rider View Post
    You have a bike that has been wrecked AND you want to run it faster than 90 mph..... even though it has head shake at that speed? Do you have a death wish???
    Don't let the fact I paid 650 for this thing throw u off. The bike is solid There was never any frame or fork damage (that I am aware of), only fairings and touch-up paint. The bike was dumped once or twice. I know quite a few older bikes that hit the road, litterally and still ride at their full potential. I think if the bikeis fixed propperly I can do 90+ safely. Until then, 85 will do.

  15. #14
    Where Am I ?
    My Bike(s)
    '87 Yamaha FZ700
    Location
    Milwaukee, WI
    Posts
    26
    Thanx K-FITT for all your help!

  16. #15
    Supporting Vendor
    Location
    La Quinta, Ca
    Posts
    754
    Could also be sticking slides.


 

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