The building of my vintage racer

Discussion in 'Airheads' started by FreeTheBeast, Apr 24, 2012.

  1. FreeTheBeast

    FreeTheBeast Shunpiker

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    I'd love some Delortos. One day perhaps. First order of business will be cylinders, pistons, heads, exhaust, and brakes. I don't think a sport cam replacement will be done this time around. Will definitely tune it on a Dyno. Max (MAX BMW) is helping me out with all this stuff. He has a Dyno at one of his shops. :thumb
    #61
  2. supershaft

    supershaft because I can

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    I am just trying to help and carbs are tied with a cam as far as the biggest bang for the buck is concerned.

    If I was racing a beemer I would put on a quick pull real throttle too. Our stock throttles are slop kings and twisting that sucker wide open is too much for the race track! IMO, they are junk as far as the race track is concerned. Nothing makes it damn near impossible to ride smooth and fast like a sloppy mile wide turn throttle! I am just trying to help and good luck!!

    When I was a little kid back before many race bikes had real race throttles, that was one of the first things we did to a bike.
    #62
  3. Boxer Metal

    Boxer Metal Mad Scientist

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    Leave the Bings for now. I would do it in this order

    1. BMW Sport Camshaft
    2. BMW Sport Pistons
    3. Carbs- 38mm Dellorto's or 36mm Mikuni's.
    4. Head Work
    5. Exhaust

    ..and I'm sure you have already removed the cylinder base gaskets:D
    #63
  4. mykill

    mykill odd

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    Cam, carbs and throttle are a good start. Hi comp 750 pistons can be tricky to find so barrel skimming and piston pocketing may be a good start.
    #64
  5. LoJack

    LoJack Long timer

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    Is there a regulation on fender size for racing? I ask because I would think you'd want a little more coverage over the top of your front wheel. As is, it's sticking kinda far up, but the top of your tire is moving twice as fast as you are. I read a report on someone taking a bicycle in a wind tunnel with an extendable fender. Slidding it forward reduced drag from a 32mm wide tire going maybe 20mph. Imagine what it would do for a 100mm wide tire going 100mph!:evil
    #65
  6. Boxer Metal

    Boxer Metal Mad Scientist

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    That is why I designed my own piston 18 years ago after I bought the last of the factory BMW Sport pistons. No base gasket, 46mm intake pocket and 10.5:1 compression:)
    #66
  7. noman

    noman Long timer

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    missed the loudon classic this year, when's the next vintage race at nhms?
    #67
  8. pommie john

    pommie john Long timer

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    I use a Yamaha TZ throttle. It's twin pull and opens 40mm dels in 90 degrees. Just right. Domino make a replica I think.
    #68
  9. pommie john

    pommie john Long timer

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    I thought I got the last pair :)
    They look like this.
    [​IMG]
    #69
  10. supershaft

    supershaft because I can

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    Your still running single plugged right mk?
    #70
  11. supershaft

    supershaft because I can

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    Great tip pj!
    #71
  12. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    I run a Tommaselli twin pull on my bike with some 36mm Dells off a Ducati, friend of mine made up some new head inlet stubs as the head is 36mm ID on the R90 heads.
    I was running a K and N filter in the stock position, then no filters now 60 mm bellmouths.
    Next its fit my new programmable ignition.:clap

    Bevel Heaven does the throttle, Dells,bellmouths etc, Steve is good to deal with. I have been unable to find better pricing on them.
    Love you bike and the vid...well cool.
    #72
  13. chasbmw

    chasbmw Long timer

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    this is a great thread, you really look as if you are enjoying yourself.

    Charles
    #73
  14. FreeTheBeast

    FreeTheBeast Shunpiker

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    http://www.race-uscra.com/events.html

    If my bike is ready, I'm also going to run it for the hill climb races in Vermont: Okemo Mt on July 6/7; August 4/5.

    MAX BMW is hosting a hill climb at Ascutney on August 25/26. http://climbascutney.com/

    :clap
    #74
  15. mykill

    mykill odd

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    Yes.
    #75
  16. Boxer Metal

    Boxer Metal Mad Scientist

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    Dual plugging is a waste of money and added weight on a 750.
    #76
  17. supershaft

    supershaft because I can

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    I can think of some race results that would make that a debatable question.

    I was just wondering. I don't guess you are having any detonation issues mk? I am still suspecting you could run higher CR dual plugged? Plus making best power at a more retarded ignition timing is always a plus. More torque times rpm.
    #77
  18. pommie john

    pommie john Long timer

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    All the quickest airheads I've seen have dual plugs. Maybe all these good tuners just do it because someone once said it was a good idea, but I doubt it.

    If you have dyno charts for the same engine with and without dual plugs I'd be very interested to see them.

    As for the extra weight.. one coil and two spark plugs? Take a piss before the race and you'll save that weight :)
    #78
  19. supershaft

    supershaft because I can

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    You should always take a piss before each race! Crashing with an empty bladder is safer than crashing with a full one just in case it springs a leak. :D When I was a kid our club asked all riders to pee before their race at the rider's meetings. I thought is a nice way of showing they cared. :D
    #79
  20. pommie john

    pommie john Long timer

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    You can usually tell which race is next up by who's lining up for the bathroom :evil
    #80