Airhead Bing tuning

Discussion in 'Airheads' started by zekedog, May 16, 2012.

  1. zekedog

    zekedog Adventurer

    Joined:
    Jun 9, 2009
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    26
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    seattle
    I live in Seattle and have spent way too much money on my Bings to have the bike still with poor mileage and constant backfire. R80st now R100st.
    Looking for suggestions for a mechanic that's great with the old Airheads and will tune them appropriately. I am willing to travel a bit if needed.
    Thanks
    B
    #1
  2. Solo Lobo

    Solo Lobo airhead or nothing

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    Hi ZD,

    Can you check and post the jet numbers. as well as the carb body numbers or as you over this engh you are done mucking about with your mixers?

    I'm sure I could swing by the station sometime with my timing light and twinmax to do some initial checks.

    Also, you do still have the Supertrapp on the bike? If so, I bet that is the source of some of the ill running.
    #2
  3. blaine.hale

    blaine.hale Long timer

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    1. Airhead forum
    2. Have you checked your ignition? Backfiring might be more a symptom of the ignition misfiring.
    #3
  4. Airhead Wrangler

    Airhead Wrangler Long timer

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    Back in Seattle, FINALLY
    If you're up to 1000cc with the original final drive, you'll probably never achieve good gas mileage regardless of how well dialed in your carbs are. Just curious, what kind of mileage are you getting?
    #4
  5. caponerd

    caponerd Kickstart Enthusiast

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    A lot of people report really unrealistic milage numbers for R100's. Mine has never gotten better than 40 mpg, no matter how I run it, and often a lot worse than that, a lot worse.
    Plus with the ethanol contaminated fuel we're forced to use these days, fuel consumption has taken another hit.

    Try this guy. Just South of Portland, but one of the best in the business, assuming you're willing to pay for quality work.
    #5
  6. supershaft

    supershaft because I can

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    +1
    #6
  7. Mista Vern

    Mista Vern Knows all - tells some.

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    Seriously, it shouldn't be that difficult. First make sure everything else is spot on - valve lash, timing, no vacuum leaks at carbs, clean air filter, etc. then order the cheap tools and instructions for setting the carbs via shorting method from here: http://www.northwoodsairheads.com/

    JT posts here often and is a good guy and his tools are superb. The instructions are very clearly written, and if after this you still have problems something more serious is going on.

    To start with I think either your valves aren't adjusted properly, you have a bad plug wire/coil, or you have a vacuum leak if you have a backfiring issue. Wish I were closer to take a look at it and give you a hand.
    #7
  8. squish

    squish Out of the office.

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    The ST had crappy MPG, I can only imagine that a R100ST would be worse.

    And I also agree with what others have suggested.

    Before you toss in the towel, make sure everything else is as good as it's going to get.

    Also look for airleaks around the carbs. Make sure the boots and other intake bits are all sealing up how they should be

    And don't overlook the ignition system, check your plugs, HT leads, coils, trigger (Bean can) and all the connections between them.
    #8
  9. zekedog

    zekedog Adventurer

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    Thanks all for responding so quickly. Very cool. To all realize please that I am no motorcycle mechanic.

    Gage.....thanks brother, I may take you up on it and no, I replaced the Supertrapp with stock.

    Airhead, howdy. Hope all is well south of the border. The bike actually does run pretty well but for the backfire with any throttle let-up. I do come off the bike smelling of exhaust though. Not as bad as with the Supercrapp. My mileage is around 30mpg. I don't have too unrealistic dreams but 35-40 seems realistic doesn't it?

    Thanks Mista and Caponerd for the leads.

    Cheers all
    Brian
    #9
  10. Wirespokes

    Wirespokes Beemerholics Anonymous

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    True! and he aint cheap!

    My R80G/S (now a liter) isn't that different from yours and it gets low to mid 40s. On the hwy I think it's about 46mpg.
    #10
  11. Solo Lobo

    Solo Lobo airhead or nothing

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    Terry,

    What carbs and jet sizes are you running in your liter G/S?
    #11
  12. amschnellsten

    amschnellsten Been here awhile

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    I fixed my Bing problems on my r100 with Mikunis. :wink:
    #12
  13. mykill

    mykill odd

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    Popping on decel is usually associated with a lean idle. Either too lean due to an air leak, leaner than stock idle jet or, most likely, too lean mixture setting.
    If everything else is as it should be, then with the bike nice and warm, slowly turn the mixture screws in or out seeking the smoothest and fastest idle. Sometimes they do run best when they pop on decel. Too rich an idle mixture makes the transition muddy and flat, too lean can make it rough or notchy.
    #13
  14. supershaft

    supershaft because I can

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    What carbs and jet sizes? The real question is what speed? Mid 40's on the highway would have to be what I call damn slow and steady. My all time record with my R100 is 42mpg and I run 130 mains in my 38mm Dell's with no pumps. 42mpg is better than I ever got with Bings but I don't think I had ever ridden that slow before. I was riding almost the speed limit that day after getting two speeding tickets on one trip. I normally get mid thirties on road trips, upper twenties around home and lower twenties if I top off after a hard ride in the twisties. It all depends.

    Bings are good carbs and very easy to tune. IMO they are way easier to tune than Mikuni's or Dellorto's mainly for fewer options. Mikuni flat slides? Most I have seen have independent floats and, just like Bing's "alcohol proof" independent floats, they are very problematic. I think anybody that fixed Bings by getting Mikuni's or Dell's were really fixing their own problems, not Bings. Bing's do not have inherent problems. Sure, Bings don't perform as well pretty much over the entire rev range or get quite as good mileage as well set up Mikuni's or Dellorto's but other than that they are great carbs.
    #14
  15. Solo Lobo

    Solo Lobo airhead or nothing

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    True, assuming the jets are the correct sizes... still need to verify that for this R80G/S within 100 slugs.... don't know about the carbs, heads and air filter yet...
    #15
  16. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Sorry, Lobo - I haven't messed around with the carbs on the G/S. It came that way, so that's the way it stayed. It was set up by a shop in SF (think it was named Darwin Motors) that converted it to a liter. They evidently did a good job.

    When I've gotten that good mileage it was riding the freeway to southern Oregon to visit friends - 300 some miles. I'm generally a bit faster than the rest of the traffic, but keep a steady pace and try to stay in the range where I won't get tickets. I'm not much of an 'on-and-off' the throttle kinda guy. Also, I'm probably 165 or 170 pounds geared up, so that makes a bit of difference.

    In the rough stuff and logging roads where I'm in lower gears all the time the mileage drops - sometimes in the high 30s.

    SS - Wonder what sort of mileage yours would get at a smoother pace? I understand it's a badge of honor what lousy mileage you get. :lol3

    You're obviously one terribly fast sumbitch! Ever think of taking it to the track?
    #16
  17. limeymike

    limeymike Who Me?

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    Bings are not complicated, I love em, easy to rebuild and for all the crying I hear on here they are easy to set up. I am always surprised when people say they solved their Bing problems by replacing with another brand of carb.
    #17
  18. supershaft

    supershaft because I can

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    My mileage isn't a badge of honor, I just mention it to point out that mileage varies a great deal on very well set up bikes. Way too much to be saying a bike "should" be getting this or that. My 42mpg was at a pretty smooth pace although I was jockying the throttle a bit to relieve the boredom.

    I grew up on race tracks. My family was in a motorcycle club that had an awesome MX and TT track on the club grounds. We would rent a county fair grounds half mile and a banked car short track for races too. Then a few other tracks but I have never been on a road course. Some of my childhood friends raced mostly MX all over the country.
    #18
  19. squish

    squish Out of the office.

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    35-40 should be doable in Washington,

    Ok
    The cool thing is as CV carbs go, Bings are about the easiest to work on.
    And if you feel so inclined there's even a Bing manual you can get from the US importer of Bing bits (I buy my carb parts from BMW dealers it's cheaper then via Bing USA, but the book is decent)

    You need to base line, which means a clean air filter, new plugs, clean fuel system from the tank vent to the hose going into float bowl.

    Make sure the bike's timing and valves are in functional order.

    If all that stuff is good then go about cleaning and resetting the carbs.
    Carbs are easy to work on. do one at a time and go slowly and you should get it to work.
    #19
  20. zekedog

    zekedog Adventurer

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    OK.....I'm in! I've been avoiding doing work myself but you are all correct.....I do need to figure this out. Hell, I've owned almost a dozen VW vans and have done a ton of work on them. How hard can it be?
    Solo.....I still may be bothering you for advice so you're not off the hook yet. You still like beer?
    B
    #20