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Thread: '91 CBR1000F won't rev out

  1. #16
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    Quote Originally Posted by mouldy View Post
    Put some new plugs in it , not revving out is a sympton of plug deteriation
    Plugs look fine-
    Black ring, inner is light brown all over including porcelain and tip. Sparks fine, sparks a long way to the head if you let it. Gaps are consistent.

  2. #17
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    Quote Originally Posted by ducatilover View Post
    Old age.
    Polish the slides and slide bores (carefully, liquid autosol works for the bores, with cotton buds)
    Hasn't seemed to improve it in my case unfortunately :-(
    I tried adding CRC to the mix and it made no difference.

    Thanks for the tip though.

  3. #18
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    Quote Originally Posted by hayd3n View Post
    you say air fliter looks fine but have you tried a run without it???
    if its better then youll know the problem
    Seemed worse without it unfortunately.
    EDIT Tried also re-sealing the air intake seal and remounting the filter in case it was not installed right and if it made a difference it was not much.

  4. #19
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    Seems to be acting a bit randomly

    After taking the slides out I blocked the breather pipe and it stopped sucking in a lot of air. Then it would rev to 10k and then suddenly release full power to the redline. But I couldn't see any difference internally when I took out the slides again.
    After Autosol + CRC on the slides it didn't do anything different, and then one time revving it up from 6k in 1st it kicked in at 9krpm to the redline but I couldn't repeat it.

    Its like an intermittent fault. For example on the last test ride after CRCing the top of the slides (vacuum part) (and a few revs in the garage) it took off and went all the way through the rev range properly once I got to a 100k area. And then it wouldn't do it again.

    Thanks for all your ideas guys.

  5. #20
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    Check the fuel tank cap breather it not restricted. If unsure crack the cap open slightly, duck tape it in place (ie it is just slightly open not sealed shut) so it will not fly open and spray you with fuel.

    Go for a ride and see if it it revs out cleanly. If it does, remove tape, shut cap and try again. If it does not rev then the breather is blocked.

  6. #21
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    Quote Originally Posted by Speedracer View Post
    Seemed worse without it unfortunately.
    another thing
    have you checked for carb boot leaks? quick test spray water on the carb boots when running and youll soon know if its leaking

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  7. #22
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    Quote Originally Posted by Speedracer View Post
    Plugs look fine-
    Black ring, inner is light brown all over including porcelain and tip. Sparks fine, sparks a long way to the head if you let it. Gaps are consistent.
    I've seen that written in a few threads, but tried new anyway. Sometimes ... it was the problem.

    Eliminate not dismiss problems.
    When life throws you a curve ... Lean into it ...

  8. #23
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    Quote Originally Posted by hayd3n View Post
    another thing
    have you checked for carb boot leaks? quick test spray water on the carb boots when running and youll soon know if its leaking
    Thanks for the tip, I hadn't heard of using water spray. I did try a gas torch (not lit) and a thorough visual inspection. I heard some obvious leaks before and fixed them (loose boots which must have been loose for quite some time) and it made no difference. Other than that I haven't found anything in this area yet.

    EDIT tried the water spray and nothing - no leaks I can find.

  9. #24
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    So does power go flat and taper off, or is it stopping dead at those revs?

    If it's stopping dead and not climbing at all, apart from random full power bursts, it sounds like a speed limiter fault and at the revs you state, that's where it'd be doing 180km/h on factory gearing, which is usually where a speed restirctor will limit RPM when there's no resistance or a short in the circuit

    What I would do, after plugs and checking the fuel pump, plus relay, is pull the speedo out and look if there's a unit with three wires in the speedo itself.
    if there is, check connections from that, to the CDI unit, take a note of what colours they are
    If you have one unusual common colour (usually pink, I think) earth it from the CDI to the frame with a resistor in there, I have a random 12v LED that seemed to work a treat on a Kawasaki system. I was having the same issues, was a prick of a thing
    Quote Originally Posted by Paul in NZ View Post
    Ha...Thats true but life is full horrible choices sometimes Merv. Then sometimes just plain stuff happens... and then some more stuff happens.....




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  10. #25
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    Quote Originally Posted by AllanB View Post
    Check the fuel tank cap breather it not restricted. If unsure crack the cap open slightly, duck tape it in place (ie it is just slightly open not sealed shut) so it will not fly open and spray you with fuel.

    Go for a ride and see if it it revs out cleanly. If it does, remove tape, shut cap and try again. If it does not rev then the breather is blocked.
    Didn't work. Thanks for the tip though.

  11. #26
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    Quote Originally Posted by ducatilover View Post
    So does power go flat and taper off, or is it stopping dead at those revs?

    If it's stopping dead and not climbing at all, apart from random full power bursts, it sounds like a speed limiter fault and at the revs you state, that's where it'd be doing 180km/h on factory gearing, which is usually where a speed restirctor will limit RPM when there's no resistance or a short in the circuit

    What I would do, after plugs and checking the fuel pump, plus relay, is pull the speedo out and look if there's a unit with three wires in the speedo itself.
    if there is, check connections from that, to the CDI unit, take a note of what colours they are
    If you have one unusual common colour (usually pink, I think) earth it from the CDI to the frame with a resistor in there, I have a random 12v LED that seemed to work a treat on a Kawasaki system. I was having the same issues, was a prick of a thing
    Interesting idea... It's not stopping dead though and the speedo goes up to 280k or so, so I don't think it was the limited edition.
    I tried manually disabling one coil (2/4 cylinders) it just climbs half as fast (if you could call it fast) through the flat spot (still climbs).
    Also tried CRCing and wiggling connectors but I didn't find any obvious problems and no difference was made so far. I'll look through the wiring diagram in the manual though... there is no speed limiting wire in the wiring diagram.
    Thanks for the tip.
    Last edited by Speedracer; 9th February 2013 at 12:45. Reason: wiring diagram checked

  12. #27
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    When I first bought My FJ ... it had similar issues. It had been imported from Japan. Carbs were cleaned and the tank lined. It had an inline fuel filter that looked ok.
    While attempting a 1000 mile rally (I completed it before the allowed finish time) ... top end power/speed was limited. On completion I removed said inline filter and cut it in half. It was VERY blocked ... to the extent I was surprised fuel actually flowed.
    New filter ... issue fixed.
    When life throws you a curve ... Lean into it ...

  13. #28
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    Quote Originally Posted by Speedracer View Post
    Seems to be acting a bit randomly

    After taking the slid


    es out I blocked the breather pipe and it stopped sucking in a lot of air. Then it would rev to 10k and then suddenly release full power to the redline. But I couldn't see any difference internally when I took out the slides again.
    After Autosol + CRC on the slides it didn't do anything different, and then one time revving it up from 6k in 1st it kicked in at 9krpm to the redline but I couldn't repeat it.

    Its like an intermittent fault. For example on the last test ride after CRCing the top of the slides (vacuum part) (and a few revs in the garage) it took off and went all the way through the rev range properly once I got to a 100k area. And then it wouldn't do it again.

    Thanks for all your ideas guys.
    holy shit that sounds exactly how my VFR400 is running
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  14. #29
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    Quote Originally Posted by FJRider View Post
    I've seen that written in a few threads, but tried new anyway. Sometimes ... it was the problem.

    Eliminate not dismiss problems.
    OK I've given it a go... Plugs replaced.
    Unfortunately this has not fixed it.
    I've updated the first post with a summary.

    Thanks for all your help.

  15. #30
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    http://www.gixxer.com/forums/showthread.php?t=106093

    Sounds like the same issue, pitty it wasn't resolved. I had intermittent running on one cylinder on my bike, coils tested ok with meter cleaned carbs checked HT leads were in spec etc. I had tested the leads without the plug boots attached, which were NGK resistor models 5K ohm I discovered the bad cylinders one wouldn't give me a reading at all, swapped it out and away we went.

    You've gone over pretty close to everything it could be, keep at it.

    Also CDI's can get leaky capacitors that can cause all sorts of worries, I've read of some guys pulling them apart and replacing bits (unfortunately the PCB is usually filled with a horrible foam/plastic goo to insulate it from everything)

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