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Thread: Fuel issue on 93'

  1. #1
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    Angry Fuel issue on 93'

    Hello everyone,

    I have a 1993 CBR900RR which I love but am having fuel issues with it. Its shutting down the fuel pump intermitantly. I have replaced the pump, relay, filter, fuel hoses, mounting hardware, you name it. It ran perfect for two days, then shut off on my way home. This time it fired back up after shaking the bike and choking the piss out of it. Ive checked continuity on the pump and relay wires but as I said it's intermitant, and it won't replicate the problem at home. This is the third pump, third filter, and second relay. Oh by the way, I've just tested the old pumps and relays and they work. Damn it. Any help would be greatly appreciated. Thanks.

  2. #2
    RRzone Elder Mikeo's Avatar
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    Default Re: Fuel issue on 93'

    Bypass the pump, run fuel line from the tank straight to the carbs and see if that helps. You can gravity feed your bike, the pump is not mandatory.
    ASMA - CMRA #118

  3. #3
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    Default Re: Fuel issue on 93'

    With this being a long term problem and being on the side of the road a few times, I've bypassed the pump a couple of times and the bike fired quickly and it got me home with no trouble. The bike runs fine without the pump, but I'm worried that if it is indeed an electrical problem, then will it start affecting something else? And the fact that I hate letting it kick my ass. Again, any help is greatly appreciated.

  4. #4
    RRzone Elder Mikeo's Avatar
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    Default Re: Fuel issue on 93'

    On my 93 I got rid of it period. I have only been on the track with it, but even at low fuel levels I have had no issues. one reason I got rid of it was because I didnt want to somehow have an electrical issue later, plus the weight savings helped me out too.
    ASMA - CMRA #118

  5. #5
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    Default Re: Fuel issue on 93'

    Thanks for the info Mikeo, at least I know I can ride my bike without worry. I'm still going to try to figure out the problem just so I can say it didn't beat me.

  6. #6
    Not been here that long isuzu327's Avatar
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    Default Re: Fuel issue on 93'

    hey man, i have a 98 cbr 900rr and i elimnated the fuel pump on mine totally and ive been riding it everyday for 3 years since then back and forth to work and where ever my wife and i want to go and have never had any issues, over 10,000 miles and never a problem

  7. #7
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    Default Re: Fuel issue on 93'

    To start off with, you guys have been great. I appreciate the info and I'm bypassing the fuel pump. So before hand I figured I'd go over all my electrical connections to make sure they were snug and had dyelectric grease in each one. Low and behold, when I unplugged the friggin rectifier the plug is slightly burnt and the plactic around three of the pins in the rectifier is slightly melted. WTF! The alternator ohm'ed out ok, and so did the rectifier but could this be the root of my fuel pump problem? Also, is this a common problem for the 900?

  8. #8
    RRzone Elder Mikeo's Avatar
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    Default Re: Fuel issue on 93'

    Quote Originally Posted by Bxtreme_25 View Post
    Low and behold, when I unplugged the friggin rectifier the plug is slightly burnt and the plactic around three of the pins in the rectifier is slightly melted. WTF! The alternator ohm'ed out ok, and so did the rectifier but could this be the root of my fuel pump problem? Also, is this a common problem for the 900?
    Huge problem witht these bikes, HUGE! Thats about all I know, I got rid of that too...
    ASMA - CMRA #118

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    Default Re: Fuel issue on 93'

    What did you replace it with? If you don't mind me asking.

  10. #10
    RRzone Elder Mikeo's Avatar
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    Default Re: Fuel issue on 93'

    Quote Originally Posted by Bxtreme_25 View Post
    What did you replace it with? If you don't mind me asking.
    I should have clarified, mine is not a street bike, so I have no charging system at all.
    ASMA - CMRA #118

  11. #11
    Not been here that long isuzu327's Avatar
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    Default Re: Fuel issue on 93'

    i dont know bout the recharging system, i dont have any problems with mine, and i havent ever had any problems with mine, but i did speak to a friend of mine that went to MMI and he is now a professional motorcycle mechanic, he says it could just be from the wiring getting to hot inside the plug and it could just cause those problems, he said it also happens more often than you might think on a lot of bikes because all of the power from the recharging system actually runs through that plug the whole time your riding, he said the best remedy to fix the problem is to get another plug with a little bigger wire preferrably #10, but thats just his opinion, but anything is worth a try

  12. #12
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    Default Re: Fuel issue on 93'

    It's a grounding problem. And Isuzu, your 98 shouldn't have had a fuel pump at all (from the factory). Not being a smartass but they stopped using pumps with the 919 motor. To the OP, if you were checking the pump while running, if you were getting intermitten signals that's because it IS getting intermitten signals. Relay is fired off the negative side of the coils and is only "hot" half the time. The other half it's a ground. Removing it as Mike suggested is a great idea. If you insist on having a pump, just remove the relay system totally. Ground the pump and run hot to wire off the ignition. When the bowls are full, it'll stop pumping. Never been to a school, but I have been under a couple
    "Crankenstein" is a GO...

  13. #13
    RRzone Elder cbr900racer77's Avatar
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    Default Re: Fuel issue on 93'

    ^^....hundred
    "Crankenstein" is a GO...

  14. #14
    Not been here that long isuzu327's Avatar
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    Default Re: Fuel issue on 93'

    i wasnt to sure bout that but it did have a fuel pump on it when i bought it, it was deff aftermarket, and a buddy told me to take it off cuz i was havin problems, and its been fine ever since, but thanks that is nice to know

  15. #15
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    Default Re: Fuel issue on 93'

    I know this is awhile later but I just replaced my petcock off my 94 cbr900rr with a vacuum actives one that is used for gravity feeding, now Iím confused. I hooked the fuel line up to the petcock and the carbs and no fuel flow is occurring. How do I get the fuel to glow to the carbs to start up the bike?

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