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Engine losing power

This is a discussion on Engine losing power within the Technical forums, part of the Caferacer.net Forums category; I have a 1971 CB500. Here's the problem in a nutshell. I start the bike, let it warm up, hop on and about a half ...

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  1. #1
    xkillerbx's Avatar
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    Engine losing power

    I have a 1971 CB500. Here's the problem in a nutshell. I start the bike, let it warm up, hop on and about a half mile down the road the engine bogs down and I lose power. Eventually the engine cuts off completely. I have to wait about 2 minute before I can start it again and then it happens all over again. I'm fairly new to motorcycle engines so try to bear with me. Any help? Thanks in advance.

  2. #2
    Senior Member krapfever's Avatar
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    Your problem could be caused by a number of things, the biggest hassle among them being the carbs.

    Before you do anything drastic like pulling the carbs and spreading their guts all over your coffee table, start by doing a little investigative work.

    1. Battery at full charge? A voltmeter is your friend.

    2. How do the plugs look? Pull all 4, you can learn a lot from a spark plug.

    3. Is the petcock clogged? Pull the fuel line at the petcock and check for flow. Be sure there are no air bubbles in the line before you reconnect it.

    Oh, and welcome to the forum.



  3. #3
    Senior Member Bateman147's Avatar
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    My GS1000 used to do that to me sometimes - turned out the gas cap vent was blocked.

    Michael

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  5. #4
    Senior Member Geeto67's Avatar
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    I bought a cb750 cheap that had that issue. Turns out the previous owner had about 300 feet of fuel line hooked up underneath the tank. I cut it down to a couple of inches and rode the bike home.

    what everybody else said - tank vent (its in the bottom of the cap), petcock, fuel line, then carbs....
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
    - Samuel Beckett
    A tool is just an opportunity with a handle
    - Kevin Kelly

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    xkillerbx's Avatar
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    Thanks for the input guys. I'll check everything out and report back. Hopefully with problem solved.

  7. #6
    xkillerbx's Avatar
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    quote:Originally posted by krapfever



    3. Is the petcock clogged? Pull the fuel line at the petcock and check for flow. Be sure there are no air bubbles in the line before you reconnect it.
    That was it. Petcock was a little clogged. Cleaned it out and everything went fine. Thanks for the advice.

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