Post your Airhead pics

Discussion in 'Airheads' started by a_k_nicholls, Sep 4, 2004.

  1. BravoFox

    BravoFox Twin With a Kick

    Joined:
    Apr 25, 2013
    Oddometer:
    1,322
    Location:
    France
    1975 Model Year, so starting in AUG 1974. (For MY74, the 90S had the earlier Dell Orto 38A without choke).

    To repeat, each European country at the time had its own definition of Model year (it was July to June in France for instance, and August to July in Germany).

    Which explains the recurrent misunderstanding if the US MY (matching calendar year) is followed: a "same" year seems to have a bike coming with different features. The bikes are actually two model years apart for BMW.
  2. gsd4me

    gsd4me 90% bluff Supporter

    Joined:
    Dec 11, 2005
    Oddometer:
    9,402
    Location:
    Brisbane, Australia
    It's true. If you hear them coming but can't see them, they sound exactly like a boxer engine.
  3. grumpyoldbstrd

    grumpyoldbstrd Been here awhile

    Joined:
    Sep 16, 2007
    Oddometer:
    730
    Location:
    Melbourne, Australia
    Curiouser and curiouser said Alice.


    Spoke to another old mate today, who’s prepared to bet his left nut that all 90S models had choke cables. He reckons that the only tickler carbs on the 90S came from people replacing worn out originals with the units from a Guzzi. Apparently these units were cheaper.


    PS. He’s now biologically redundant, and can afford to lose his left nut.
    eight90eight and Planetducky like this.
  4. getonyourbikeandride

    getonyourbikeandride Been here awhile

    Joined:
    Dec 28, 2015
    Oddometer:
    290
    Location:
    New England
    Just because they happen to be a twin with equally spaced firing intervals does not make it 'like a boxer'. The engine vibration, torque reaction when you blip the throttle and the crankshaft orientation all cause different effects on the chassis behavior (not to mention chain versus shaft drive).

    So yes, blaspheme!
    Disston, SmittyBlackstone and CNRED like this.
  5. dirtdreamer50

    dirtdreamer50 long time rider

    Joined:
    May 12, 2010
    Oddometer:
    5,021
    Location:
    texas coast
    Guess take it up with BMW then. Was just repeating what I read on their site. Thought it interesting, that's all. dd50
  6. BravoFox

    BravoFox Twin With a Kick

    Joined:
    Apr 25, 2013
    Oddometer:
    1,322
    Location:
    France
    I'm not really interested in the debate (I'm a Series 7 kinda guy anyway :johntm), but I have only one word for your friend: SOURCE.
    We live in a time where opinions become reference frames, but I'm from a school of thought which promoted the curious, sceptical, and inquisitive mind. :beer
    ME 109 and radmeister like this.
  7. ricard

    ricard Been here awhile

    Joined:
    Aug 11, 2006
    Oddometer:
    272
    Location:
    Los Angeles
    Mulholland Highway

    DA805131-FFA3-45C4-934D-C7588C191847.jpeg
  8. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    6,360
    Location:
    New Zealand
    There is nothing special needed to make a parallel twin fire at 360...that's just the normal way they run.
  9. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,829
    Location:
    Providence, RI
    Well, not to be argumentative, but Triumph parallel twins run in either 360 and 270 degree firing patterns, and 270 is actually becoming the more common design.

    You can also find parallel twins that run with a 180 deg firing order.
  10. RideDualSport.com

    RideDualSport.com Zut alors!

    Joined:
    Jul 7, 2009
    Oddometer:
    2,197
    Location:
    Texas / France
  11. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,829
    Location:
    Providence, RI
    ^ Could have been straight out of a BMW ad...
    Uke, SmittyBlackstone and fxray like this.
  12. BravoFox

    BravoFox Twin With a Kick

    Joined:
    Apr 25, 2013
    Oddometer:
    1,322
    Location:
    France
    A rare blue R100RS MotorSport


    R100RS Blue Motorsport 13.jpg
    BIG^DALY, Planetducky, Uke and 11 others like this.
  13. getonyourbikeandride

    getonyourbikeandride Been here awhile

    Joined:
    Dec 28, 2015
    Oddometer:
    290
    Location:
    New England
    Well the straps around the factory bags could lead to embarrassing questions @ the dealerships...
  14. Jimkav

    Jimkav Been here awhile

    Joined:
    Jan 8, 2015
    Oddometer:
    183
    Location:
    Long Beach ca
    623C62F6-D117-4CB6-BD27-F338386D73B2.jpeg PCH Sunday afternoon
  15. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    6,360
    Location:
    New Zealand
    They are ''special'' firing patterns, but normal for a vertical twin , and a 180 flat twin...is 360 degrees. You could ''make'' a BMW fire 270...but why ?
  16. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,829
    Location:
    Providence, RI
    Perhaps you don't want to keep going with this, if so, my apologies, but if you do, then this is a very concise explanation of the parallel twin firing order pros and cons...

    Simon Warburton, Product Manager for Triumph Motorcycles Ltd. at the home office in Hinckley, has forgotten more about the pros and cons of various parallel-twin crankshaft configurations than most mortals will understand in a lifetime, so listen up. "If the engine speed is high," he says, "a balance shaft will be required to cancel out rocking couple. A 180-degree crank offers the most uneven firing interval: 180 and 540 degrees. It also gives the lowest pumping losses, as displacement in the crankcase remains roughly constant throughout the cycle. The 360-degree crank gives even firing, but as both pistons move together offers the same mechanical balance as a single (i.e. not very good). Again, balance shafts are required. The 360-degree firing interval has the advantage that only one ignition system is required, with a wasted spark.


    "The 270-degree crank has a firing interval of 270 and 450 degrees, the same as a 90-degree V-twin. Therefore, this sounds and feels like a 90-degree V-twin. It's a compromise between the 180 and 360 configurations: better primary balance than the 360 and a lower rocking couple than the 180, but it still requires balance shafts at high engine speeds. _ "Another benefit is that as one piston is stationary, the other is moving. This gives a dynamic benefit whereby the crank speed fluctuates less during a cycle. Yamaha uses this effect on the crossplane R1 crank. On both the 360 and 180 cranks, both pistons are stationary at the same time."_

    https://www.motorcyclistonline.com/how-to/parallel-twins-and-sportbike-testing/
  17. Jimkav

    Jimkav Been here awhile

    Joined:
    Jan 8, 2015
    Oddometer:
    183
    Location:
    Long Beach ca
  18. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,829
    Location:
    Providence, RI
    ^ That's really pretty...
    Jimkav and SmittyBlackstone like this.
  19. SmittyBlackstone

    SmittyBlackstone Been here awhile

    Joined:
    Mar 3, 2015
    Oddometer:
    614
    Location:
    Westchster County, NY
    Finally got a /2.

    It is a whole different world of motorcycling. 5620533.jpg
  20. getonyourbikeandride

    getonyourbikeandride Been here awhile

    Joined:
    Dec 28, 2015
    Oddometer:
    290
    Location:
    New England
    Classy, slow and steady!
    Uke, SmittyBlackstone and lucky6600 like this.