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Thread: 85 R80 stalls when throttle applied from idle

  1. #1
    Registered User jimbc's Avatar
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    85 R80 stalls when throttle applied from idle

    The engine of my 85 R80 intermittently stalls when I open the throttle to accelerate from a stop. I was able to duplicate the concern while standing beside the bike and noted a popping sound and saw a puff of smoke from the right carb.

    It concerns me when it happens at a intersection when the light turns green.

    I'm posting this because I'd like to understand what's happening when it stalls and why. Thanks for your input.

    Jim
    1985 R80 Original owner

  2. #2
    Administrator 20774's Avatar
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    Sounds like maybe your idle circuit needs tweaking or you need a carb synch. Try changing the idle air mixture screw small turns (1/8 to 1/4) in one direction on both carbs. See if the problem improves or gets worse. If you find one direction helps, then consider checking the entire carb synch process to get it dialed in better.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Registered User jimbc's Avatar
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    Thanks Kurt
    1985 R80 Original owner

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    Registered User lmo1131's Avatar
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    JIm, when was the last time you went through the ignition adjustment / plugs/ valves drill? It's always nice to know when everything is "zeroed" out.

    The last time I encountered a "popping and spitting" situation it turned out to be tiny bit of grit that found it's way to the right side main jet. When was the last time your carburetors were off and cleaned?
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  5. #5
    Registered User jimbc's Avatar
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    Thanks Lew. The last time the carbs were done was 2008. I plan on taking the bike to the local airhead tech for this and to have the splines lubed for another problem I'm having. In the mean time I'm trying to gain an understanding of what's going on. Jim.
    1985 R80 Original owner

  6. #6
    Luddite Looney wecm31's Avatar
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    Where are you in Ontario??

    I'll be hosting a Tech Day at my place near Eganville (Ottawa Valley) June 22/23.

    I'm sure our collection of experts could verify your carb tuning and even get
    those splines lubed, all within our body of past experience.

    Check your Airmail for details of shoot me a PM...
    Gerald P
    The last thing I want to be is just like everyone else...
    1985 R80RT
    1969 Sport Fury Convertible

  7. #7
    ONE LESS HARLEY 04r1150rs's Avatar
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    most likely it's a lean stmble when opening the throttle, try backing out the air fuel idles screw about 1/16 of a turn, see if that helps.
    Richard
    2004 R1150RS
    1984 R80 G/S
    2003 Suzuki DRZ 400S

  8. #8
    Registered User jimbc's Avatar
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    Thanks Gerald, I will consider the June weekend. I like your plate, mine is R80. 85R80 was an alternate choice when I applied for mine way back when.

    And to Richard thanks, like Kurt suggested, I could try some small adjustments myself.

    Cheers

    Oh yea. Gerald, I'm close to Cobourg
    1985 R80 Original owner

  9. #9
    R100GS, '89 Guenther's Avatar
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    I would check the diaphragm in the right carburetor. The diaphragm is moved up-and-down by the pressure difference caused by the different speed of the air through the carburetor tunnel. At low throttle opening there is less air per second going through which causes a minimal pressure difference between both sides of the diaphragm and hence the jet needle attached to the diaphragm hangs low and thus only a small amount of fuel evaporates into the airstream. Under full throttle opening the large amount of airflow causes a vaccum in the dome above the diaphragm and hence the jet needle is raised and more fuel is entering the tunnel.

    This techique gives a pretty good air-to-fuel ratio at all throttle positions given no modern schnick-schnack (fuel injection, senors-sensors-sensors, electronic control).

    If the diaphragm is torn a sudden opening of the throttle would not cause the diaphragm to lift and you have a far too lean air/fuel mixture. Depending on the damage of the diaphragm it may eventually regain position in relation to the throttle position and airflow per second.

    A story: When I rebuild my R100GS' carburetors back when I didn't watch carefully when I positioned the diaphragm under the dome in the carburetor. There's a notch that is used to align both. In my case it was off (turned) by a couple of degrees. The motor reacted erractically at low throttle positions but worked pretty normal at above 2,000 RPMs.

    /Guenther

  10. #10
    Administrator 20774's Avatar
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    In the past, I've heard people report that their bike seemed to run fine at lower speeds but couldn't go above a certain speed. Typically, that's due to a torn diaphragm where at the higher speeds and higher vacuums, the tear doesn't allow the equalization. Plus at higher speeds, the idle circuit is less effective. But at lower speeds, while the raising and lower of the slide is important, the idle circuit is still contributing which could be the reason a bike might run OK at lower speeds with a torn diaphragm. So, I would think that if the bike runs well at freeway speeds, it's probably not the diaphragm. We never heard about that from the PO.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  11. #11
    Registered User jimbc's Avatar
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    Thanks for your input Guenther. Other than the stalling the engine runs great.

    Kurt. Thanks. You must spend a lot of time on this site.

    Cheers
    1985 R80 Original owner

  12. #12
    Administrator 20774's Avatar
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    Hey, I'm willing to throw an opinion out there...it's up to others to figure out if it's worth a darn!
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Worth a darn

    Kurt,

    I think your ideas ARE worth a darn!

    After reading each one, I say "Darn that Kurt!"

    Just kidding!!

    I always am better off after reading your comments and suggestions. All are very appropriate.

  14. #14
    R100GS, '89 Guenther's Avatar
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    It is always helpful for others to know when the problem started, was any service/maintenace done before and in this case ... does it eventually run without stalling?

    /Guenther

  15. #15
    Registered User jimbc's Avatar
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    It starts, idles and runs fine at any rpm but when I grab some throttle to accel from a stop is when it intermittantly stalls
    1985 R80 Original owner

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