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Thread: Carb question: Attention Canadians!!

  1. #1
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    Carb question: Attention Canadians!!

    While sorting out all the part numbers of all the stuff I need to buy for the winter maintenance on my 1987 R80, I noticed that my carbs are numbered 64/32/353A & 354A. A little research turned up that the "A" carbs were used on the R80's in Europe restricted to 20 KW.
    Have any other Canadian owners noticed this "A" on their carb bodies? Is it really possible I have a power restricted bike?

    Second question for ALL airhead owners: Anybody used to Motobins Carb rebuild kits? Are they as good as the Bing stuff? They seem so cheap in comparison I thought I should take an opinion survey before I order anything.
    "Better is the enemy of just good enough"

  2. #2
    Luddite Looney wecm31's Avatar
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    I have an 85 R80RT, pretty sure it was shipped as a Canadian model, ie Kilometers on the speedo. But I don't have the A carbs you refer to. A friend has an 86 European bike, it has a different lighting setup. The headlight is only on when you switch it on, the running light is just the white marker above the headlight. And IIRC....European bikes don't have the pulse air system. My bike does have it. As for Motobins, I haven't used the carb kits but bought other items from them (exhaust) and price and shipping was decent.
    Gerald P
    The last thing I want to be is just like everyone else...
    1985 R80RT
    1969 Sport Fury Convertible

  3. #3
    blah blah blah squiffynimrod's Avatar
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    Both my 85 and 92 are CDN bikes, neither have an "A" designation on the carbs.

    Keep us posted on the Motobins carb kits, it's probably next winter's project for me.
    1985 R80RT/ 2002 R1150GSA
    IBA # 44032

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    I have a call in to the local BMW dealer to see if they can shed some light on this. According to Bing, the "A" carbs have a 110 main jet where the non "A" units have a 135. There also seems to be some mechanical restriction on how far open the throttle can be. Who knew!?! I guess I should open a carb up to see what mains are in there. Mysterious. On the bright side, maybe I'll suddenly get another 20 or horsepower out of my bike with the proper carb setup!!
    "Better is the enemy of just good enough"

  5. #5
    Registered User PeoriaMac's Avatar
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    maybe I'll suddenly get another 20 or horsepower out of my bike with the proper carb setup!!

    If you can get 20 more HP from an Airhead with carbs alone, you should have been working for Butler and Smith....

    mac
    Mac
    1986 R80RT, 2005 R1200GS
    Livin' Large On The Lake

  6. #6
    blah blah blah squiffynimrod's Avatar
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    Quote Originally Posted by G_Thomas View Post
    I have a call in to the local BMW dealer to see if they can shed some light on this. According to Bing, the "A" carbs have a 110 main jet where the non "A" units have a 135. There also seems to be some mechanical restriction on how far open the throttle can be. Who knew!?! I guess I should open a carb up to see what mains are in there. Mysterious. On the bright side, maybe I'll suddenly get another 20 or horsepower out of my bike with the proper carb setup!!
    So that means.....................I can make as much HP as an S1000RR!

    110 mains to 135 mains= 20 hp.
    1.25 hp gain for each unit of carb main.
    R100RT= 60 hp
    S1000RR= 192 hp.
    Difference of 132 hp/1.25=105.6
    105.6+135= 240.6

    Is there a kit or mod to run 240 main jets on my R100?
    Should be cheaper than buying a S1000RR!

    1985 R80RT/ 2002 R1150GSA
    IBA # 44032

  7. #7
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    Engines 101

    Some of you might have missed a subtle but important point.

    The normal 50 hp engine output is based on a carb with 135 mains and the the corresponding amount of air. For some markets the engine was DE-TUNED from 50 hp down to around 25 hp by decreasing the amount of air and fuel allowed into the engine (smaller mains and restricted throttle opening).

    I was not suggesting that switching to larger main jets will give me a 70 hp airhead. That is preposturous. Quite laughable actually. Changing carburation AND adding a supercharger (among other required changes) to gain power, now we are talking.
    "Better is the enemy of just good enough"

  8. #8
    Registered User photorider's Avatar
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    Interesting. I also have the "A" stamped on the carbs of a '96 R80GS I bought in Latin America.
    76 R60/6
    97 R80GS

  9. #9
    Benchwrenching PGlaves's Avatar
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    Drop the float bowls. Lie on your back. Look up. Read the number on the main jet.

    If you have the little jets you will have to look further because if both the air and fuel are restricted then simply replacing the jets won't solve the problem. You need to find and eliminate the air restriction, however they did that. Probably with a different wide-open throttle stop. Maybe with a different slide cutaway. I don't know.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

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    "eliminate the air restriction, however they did that"

    Believe it or not, air restriction was acheived by using a different carburator top! Could get a little spendy to convert these.
    But first, I am going to open up a carb tonite and see what's in there for a jet. Maybe the PO just used the "A" bodies and already made the conversion.
    Hopefully the dealer will (eventually) help me out with this mystery. They aren't winning any service awards lately....but that's a different story.
    "Better is the enemy of just good enough"

  11. #11
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by G_Thomas View Post
    "eliminate the air restriction, however they did that"

    Believe it or not, air restriction was acheived by using a different carburator top! Could get a little spendy to convert these.
    But first, I am going to open up a carb tonite and see what's in there for a jet. Maybe the PO just used the "A" bodies and already made the conversion.
    Hopefully the dealer will (eventually) help me out with this mystery. They aren't winning any service awards lately....but that's a different story.
    A different top could limit the movement of the slide upwards.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  12. #12
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    Bingo!
    "Better is the enemy of just good enough"

  13. #13
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    Well. My carbs have the proper 135 main jets (for Canada/UK) and the slides open all the way, so.......Who knows. Either the factory or the PO must have cooked up these hybrids somewhere along the way.
    Freaky.
    Thanks for the responses.
    "Better is the enemy of just good enough"

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