'82 GL500I, no power under load.
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Thread: '82 GL500I, no power under load.

  1. #1
    Senior Member Cobram's Avatar
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    '82 GL500I, no power under load.

    Put away last winter as usual with fogger, fuel stabil, gas additive, carbs run dry and fogged right at starvation.

    Five of so years ago installed Larry Carbs on her. I got used to pulling the bike out of storage in the Spring, doing little more than wiping the winter mold and evicting whatever vermin was occupying it without paying rent. Always sparked right up and a normal pre-flight and all was usually good for the season.

    Well, not so problem free this year. She started right up, idled beautifully, accelerated nicely….but has low power under load. Once in gear and moving, punch the throttle and you’re back on your old Briggs and Stratton’d mini bike from your misspent youth.
    I can milk it by winding the piss out of it and riding the clutch until it gets up to speed a bit…barely driveable. In neutral or cruising in lower gear, she’ll go right to redline. No backfiring, nothing out of the oridinary except the lack of power.

    Took it out on the highway after a fresh tank of gas and adequate amount of sea foam, with the bike at full throttle in 5th I was being passed by MBTA busses in 2nd gear, bike would not go over 65MPH at full throttle over a 4 or 5 mile stretch.

    Decided to balance the carbs, they balanced rather nicely, made ZERO difference with the lack of power under load.

    Pulled the carbs, found the mixture O-rings were in pieces…but she idled fine.

    Pulled the air cutoff valve off and it was very swollen (thank you ethanol) and had a big rip in it.

    Checked all the passages, jets, emulsifier holes etc. all were very clean and unblocked. Sprayed carb cleaner into every orifice I could find (on the carbs.) Did not find one blockage. Accelerator pump squirted nicely, once into each eye, spray was very uniform as the sting in each eye was equally painful.

    Took carbs apart and dumped everything into the ultrasonic cleaner.

    Installed new air bypass valves.

    New O-ring and washer for the mixture screw. I am only posting because I thought I’d find SOMETHING in the carbs to explain what’s going on. Everything I’ve checked looked good, and what didn’t shouldn’t cause the no power situation. I’ve had torn air bypass valves which didn’t cause symptoms of anything.

    The obvious was all done, plenty of fuel supply to carbs, new air cleaner, cleaned air box screen, dumped drain valves, rod mod to new plug caps, iridiums look new etc.

    Put the rebuilt (ultra cleaned) carb back on, and SAME THING. No difference, none, nothing nada. Throttle and acceleration are acting the same, bike can’t get out of it’s own way at a stop, can milk it to get it going, and ride it, but it has absolutely no balls under load.


    NEXT…?? Any ideas? The engine sounds fine, she was running perfectly when put away in the winter. Doing a compression check just for the hell of it (it was fine, feels fine, probably still fine) I’m going to just start swapping out parts with my parts bike (coils, carbs, friggin engine if it gets to it) until I can figure this one out. Exhaust back pressure feels normal, LED inspections shows what can be seen down the exhaust pipe is unobstructed.
    1978 CX500 X 2
    1982 GL500I

    I live on a one-way street that's also a dead end. I'm not sure how I got here, or how I'm going to get out.

    Four wheels move the body; Two wheels move the Soul.

  2. #2
    Super Moderator CXPHREAK's Avatar
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    Did you check the airfilter for freeloaders Steve?
    Rebuilding Handlebar Switches

    http://s1085.photobucket.com/user/CXPHREAK/library/Switchgear%20rebuild?sort=6&page=1

    Rider 81 500C, Thingy Born a 78Z. Ozdeluxe born an 80 shadow.

    GET A MULTIMETER RTFM I am a CX500. If you maintain me I will run forever.

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  3. #3
    Senior Member Cobram's Avatar
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    Yeah, as I mentioned above, new air filter, emptied the airbox drain hose, and even cleaned the airbox screen with brake clean and blew it out with compressed air.

    Quote Originally Posted by CXPHREAK View Post
    Did you check the airfilter for freeloaders Steve?
    1978 CX500 X 2
    1982 GL500I

    I live on a one-way street that's also a dead end. I'm not sure how I got here, or how I'm going to get out.

    Four wheels move the body; Two wheels move the Soul.

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  5. #4
    Super Moderator CXPHREAK's Avatar
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    How did I miss that?. the bike is CDI?
    Rebuilding Handlebar Switches

    http://s1085.photobucket.com/user/CXPHREAK/library/Switchgear%20rebuild?sort=6&page=1

    Rider 81 500C, Thingy Born a 78Z. Ozdeluxe born an 80 shadow.

    GET A MULTIMETER RTFM I am a CX500. If you maintain me I will run forever.

    http://cx500forum.com/mediawiki/inde...itle=Main_Page

  6. #5
    Senior Member Cobram's Avatar
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    Naw, it's an '82 GL500I.

    Quote Originally Posted by CXPHREAK View Post
    How did I miss that?. the bike is CDI?
    1978 CX500 X 2
    1982 GL500I

    I live on a one-way street that's also a dead end. I'm not sure how I got here, or how I'm going to get out.

    Four wheels move the body; Two wheels move the Soul.

  7. #6
    Senior Member monsoon392's Avatar
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    how is your charging voltage looking? im sure you have checked but just in case... im dead curious as this is my exact motorcycle too!
    1982 HONDA GL500 Interstate 55K+
    FACTORY SERVICE MANUALS

  8. #7
    Super Moderator CXPHREAK's Avatar
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    Not familiar with GLs.

    If TI I would suspect the advance unit has jammed.
    Rebuilding Handlebar Switches

    http://s1085.photobucket.com/user/CXPHREAK/library/Switchgear%20rebuild?sort=6&page=1

    Rider 81 500C, Thingy Born a 78Z. Ozdeluxe born an 80 shadow.

    GET A MULTIMETER RTFM I am a CX500. If you maintain me I will run forever.

    http://cx500forum.com/mediawiki/inde...itle=Main_Page

  9. #8
    Senior Member Cobram's Avatar
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    I have a very large hammer, where do I hit it to un-jam it? ;-) I'll look it up tomorrow.

    Quote Originally Posted by CXPHREAK View Post
    Not familiar with GLs.

    If TI I would suspect the advance unit has jammed.
    1978 CX500 X 2
    1982 GL500I

    I live on a one-way street that's also a dead end. I'm not sure how I got here, or how I'm going to get out.

    Four wheels move the body; Two wheels move the Soul.

  10. #9
    Super Moderator CXPHREAK's Avatar
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    Check it with a timing light Steve.
    Rebuilding Handlebar Switches

    http://s1085.photobucket.com/user/CXPHREAK/library/Switchgear%20rebuild?sort=6&page=1

    Rider 81 500C, Thingy Born a 78Z. Ozdeluxe born an 80 shadow.

    GET A MULTIMETER RTFM I am a CX500. If you maintain me I will run forever.

    http://cx500forum.com/mediawiki/inde...itle=Main_Page

  11. #10
    Senior Member Brian Sams's Avatar
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    If you do a leak down test and it looks fine, I'd still be suspicious of the fuel flow. I don't know how you would check fuel flow while under load , but it sounds to me like a fuel flow issue, like the tank isn't vented properly, or there's some obstruction that allows enough fuel to seem like it is sufficient without providing enough for the engine under load.

    I'm trying to think of an electrical problem that is consistent with the symptoms, and I guess that you already brought up everything I could think of. Did you try removing one of the plug wires while under load and seeing if it has any effect?
    78 CX500 Cafe Project 99% Complete
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