R100GS missing on start

Discussion in 'Old's Cool' started by Rapid Dog, Feb 8, 2007.

  1. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    couple o questions.
    when I crank my GS over cold it starts up but runs on one (left) cylinder for the first few rpm's then the right side kicks in. After that it runs fine.
    Could this be a plugwire?
    I have the moto electik NGK wires but they are not brand new.

    Also, I noticed that the choke levers at the carbs don't seem to want to return on there own with the existing return springs when I move the choke lever back to off position.

    Should I assume that it's just gummed up at the carbs, or is there somthing I should know about the bowden cylinder under the tank?
    I cleaned and lubed it during my re-furb.

    My old bike (1978) had the direct cable/lever on the side of the airbox so I'm not familiar with the gremlins of the bowden cylinder...
    #1
  2. R-dubb

    R-dubb Dubbious Adventurer

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    They stick at the carb. You can test this by making sure the cable moves freely when the lever is held up by hand. It's possible you kinked the cable, but given the starting problem, I'm betting on gummed up carbs. When is the last time your carbs were treated to a new set of o-rings? Sounds to me like one jug is not getting fuel on start-up. You could have a blocked pilot or simply vacuum leaks around the o-rings.
    #2
  3. Solo Lobo

    Solo Lobo airhead or nothing

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    Check that your chokes on both cylinders are engaging.

    Mine did that and I found one cable had broken!
    #3
  4. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    both are moving as they should, but they don't return by themselves all the way. a slight push on the lever returns them, but they do feel some resisteance (gum?)...

    The only thing I've done to the carbs is a cleaning of the intakes/slides/bowls and new diaphrams.

    I don't believe the cables are kinked.
    #4
  5. datchew

    datchew Don't buy from Brad

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    it would be quick and easy to check the continuity of the plug wires with a multimeter.
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  6. R-dubb

    R-dubb Dubbious Adventurer

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    Need new o-rings, a clean pilot jet and choke circuit.
    #6
  7. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    which o-rings exactly? can you buy all these parts seperately or do you have to buy a complete carb kit(s)?
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  8. andmoon

    andmoon Long timer

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    Mine did that when she had a cracked coil.
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  9. R-dubb

    R-dubb Dubbious Adventurer

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    buy a carb kit that does not include diaphrams. (That would be a #1 kit.)

    http://www.bingcarburetor.com/bmw/bmwcvkits.html
    #9
  10. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    done. Bing #1 kit (no diaphrams) $37 shipped.

    Thanks...I'll concentrate on the carbs before I worry about the spark.

    Incidently I have, besides the NGK wires, the ME brown coil and new plugs.
    #10
  11. willyt

    willyt Adventurer

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    92 PD that did the same thing... one cylinder until the coil heated up. New coil fixed it.
    #11
  12. wintonio

    wintonio last of the Dum Dum Daze

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    wow! I just called Bing, and asked about the #6 kit, full rebuild, $154 :eek1
    then I asked about the #4 kit, sans floats and pivot pins, $113 :huh. I thought, well, Fuck ME! I graciously bowed out of the conversation with my stumbling thru the phrase "Let me call you back... I thought for some reason it was like $50..."

    Now then, anyone have any suggestions on how to tell if I need new floats, etc, or a cheaper place to buy the stuff?
    #12
  13. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    ....don't assume you need a complete carb rebuild.
    ask yourself:
    how long has the bike been sitting?
    how many miles is on it?
    does the bike start and run?
    are you mechanically addept? you can f'm up worse if you don't pay attention.
    may as well send them off and have them done for you as an alternative...

    read Oak's article on rebuilding airhead CV carbs on airheads.org....he 'splains
    the #1 kit may be all you need if that, at $37 shipped.

    keep in mind that the diaphrams in the next kit run about $18 each at the dealer, 20% off if you go thru Chicago BMW. Full kits run about $50 +- from a dealer.

    it's weird that they don't advert prices on their website...

    go slow, concentrate on one thing at a time :freaky
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  14. wintonio

    wintonio last of the Dum Dum Daze

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    well, I may be getting a bit out of hand here with all this spending. I guess because I don't know a whole lot about how exactly things should be, and what is adequate, I just assume to myself that I should replace everything and start off fresh and all that crap, BUT, (and I hate to admit this)

    YOU ARE RIGHT, AND I WILL TAKE YOUR SAGE ADVICE. THANK YOU.

    I would imagine that not everything is shot, and that I should open it up first and see how things are in there. Part of my willingness to go ahead and get new stuff right now is not just bad habits, it is because I am getting 28-30mpg, which sucks real bad. I know I will never get super great mileage here, but it has got to be better than that. In any case, I need to remember that BMW owners are cheap ass bastards, and if I want to be a real owner, I need to tighten things up, get real thrifty and what not.
    #14
  15. Solo Lobo

    Solo Lobo airhead or nothing

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    I am sure that you know this, but to put it out there again....

    The BMW kits do not come with the needle and needle jet. If your bike is around 40-ish miles replace these as the are a part that does wear out.

    Additional foot note, the little rubber tipped jobbers actuated by the float are freekin expensive, I think something like $13 each... I would ony replace these float needles if your carbs leak.
    #15
  16. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    ...so, what IS the history on the bike?
    info and pics will reap volumes of sahge advce here...dude.:norton
    #16
  17. wintonio

    wintonio last of the Dum Dum Daze

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    ok, I will take my work camera home, and take a bunch o piccies for the zen masters here, and then I will both bore and confuse you with my poorly worded questions, where I will inevitably not know the correct terminology, and in the interim I will begin to fight my super duper excessively strong obsessive compulsive desires and wants and fixations and I gotta have it right now type thinking and general mentality. I think I am hardwired to be the kind of guy that instinctively wants to pour gasoline on a fire, both figuratively and literally...

    Another thing: I found out yesterday that the parts manager at the ratty and rundown looking BMW dealership near me is an AIRHEAD guy, and I am taking my carb to him, so he can tell me what I need. I will, however, also take Solo Lobo's advice and get new needles and needle jets.

    edit: the PO is the father of my friends baby mama. He is a good guy. Clang looked at the bike a while before I bought it, though not for me, and he told me that it looked like a pretty good bike. The PO had it for a few years in CO, and the PO before him lived in Lake Havasu, I believe. I need to find him and contact him, and see what he did. All the PO I bought it from could tell me was that the engine was rebuilt before he got it, that it had a new speedo with 6500 miles on it, and that he thought the speedo was replaced when the engine was rebuilt. I don't think he rode it a whole lot, certainly probably not in the rain (like I do), so I am sure he had no knowledge of the cracked ignition coil. He is the kind of guy that would have told me of anything that was wrong, that he was aware of; I have just had a few crap outs, like a cracked coil, dying battery, broken clutch cable, typical stuff... but I also like to root and remove
    #17
  18. lkchris

    lkchris Albuquerque

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    Running on one cylinder at start isn't much to worry about.

    It's really just a difference in effectiveness of the aux carbs (chokes) and possibly related to air leaks. Could even be a difference in compression between cylinders.

    Since both cylinder spark plugs fire simultaneously, they're both getting the same spark barring a really bad wire. Ignition, nevertheless, is very unlikely a problem related to this symptom.
    #18
  19. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    Thanks for that. Since my choke levers seem to be sticky (don't return by themselves via the spring) I'm going to assume that's the problem.

    I'll post once I find out for sure.
    #19
  20. andmoon

    andmoon Long timer

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    coil
    #20