how to increase r100 power

Discussion in 'Airheads' started by Nath87, Oct 19, 2012.

  1. Nath87

    Nath87 Adventurer

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    I'm thinking about making a cafe racer out of a r100/7. I would like the bike to have more than stock 60 hp and 54 lbft torque is it possible to get much more horsepower out of the old air heads with out making them over heat?
    #1
  2. mykill

    mykill odd

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    Yes, it is possible.
    #2
  3. Airhead Wrangler

    Airhead Wrangler Long timer

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    Don't worry, your wallet will overheat before the bike does. :D
    #3
  4. KhaoSanMan

    KhaoSanMan Airhead

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    #4
  5. chasbmw

    chasbmw Long timer

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    Note the costs.............and this was done a number of years ago!

    The variety of cams, pistons, ignitions that are available now is very wide and if you are not careful we will end up with a repeat of the great 336 flame war................look at posts by RG gregor and pommie john for some ideas and interesting threads.

    You cant go far wrong with a high compression dual plugged engine with a slightly more spritely cam and some port work, if done properly, by someone who knows what they are doing, you will be pleasantly surprised.

    And if you are going to improve the engine, you might want to consider brakes and handling, in which areas BMW were somewhat lacking when new, let alone after 35 odd years!

    Charles
    #5
  6. mykill

    mykill odd

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    Really good point.
    The best money spent to go the fastest is suspension and diet for both you and the bike. After that cam, compression, porting, carbs and a well designed exhaust will free things up. The number of combinations will rival oil threads in opinions.
    #6
  7. Rob Farmer

    Rob Farmer Long timer

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    Step this way young man. Look at the pretty things and see how they sparkle :evil

    http://www.moorespeed.co.uk/moorespeed/bmw-tuning
    #7
  8. supershaft

    supershaft because I can

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    Most agree the biggest bang per buck is either a new cam or carbs. I think the cam wins out simply because most people aren't very good at jetting. I put just a 336 in my bike first and loved the results. Other inmates here really like their 336's too. The very first hot rod part(s) I got was a close ratio gear set. Personally, if I were you the first hot rod parts I would get would be Brembo brakes forks and a late model ('81 on) clutch and flywheel. Start at the beginning I always say. Good luck!
    #8
  9. bikerfish

    bikerfish flyfishandride

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    buy a K100
    #9
  10. Boxer Metal

    Boxer Metal Mad Scientist

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    I agree. Once everything else is done and you are outriding the power you have then go bigger and better.
    #10
  11. robtg

    robtg Been here awhile

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    Lighter throttle springs......:wink:
    #11
  12. supershaft

    supershaft because I can

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    Lighter springs? But still be careful cranking that thing wide open. A freind of mine from back home came out here and broke a throttle cable trying to get his bike to run with mine. He said he kept hoping there was more. There wasn't. :lol3
    #12
  13. supershaft

    supershaft because I can

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    I think I've done better than that.
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  14. orangebear

    orangebear Long timer

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    my dad use to run a 79 r100/7 and said he use to sit at 90mph on long runs and said the top speed was great even tho the bike handle bad. i thought the book top seep for one was like 130ish mph
    #14
  15. Rob Farmer

    Rob Farmer Long timer

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    You're thinking of the RS or CS machines. These came in around 125Mph

    The early 100/7 was much slower with a soft engine and small carbs. I have one, it used to rev it's nuts off at 90 until I fitted a 33/11 final drive. If you want top end performance you need to get the compression up and it breathing better.

    We don't know what year the machine is that the OP owns but if he's quoting 60Bhp it's probably a 81-84 machine.
    #15
  16. RGregor

    RGregor Been here awhile

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    Hi!

    Getting more than 60hp out of an R100 engine is easy.
    But first of all you should decide where in the rpm range your engine should be stronger. Low - medium - high rpm?
    That will affect the direction you' ll have to take and prevent you from building an engine you won't like.
    Then you should consider that your talking about tuning an engine that is nearly 40 years old.
    How many miles has it already run? No sense to try to tune a worn out engine.
    Blueprinting an engine is no bad idea as a starting point for improvements.
    And of course the question about the budget you have.

    Any chance to ride a modified / tuned beemer?
    That gives you a better impression of what you might get than anyone can give you here with words.
    #16
  17. bikerfish

    bikerfish flyfishandride

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    my /7 wouldn't do 130 if it was dropped out of a plane!
    #17
  18. chasbmw

    chasbmw Long timer

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    A R100 would do something in the region of 105-110, on the speedo, which in most cases is around 10% optimistic, not that bad for an engine producing less than 50 RWHP. Handling tends to get interesting at speeds over 110, even when the bike is set up correctly
    #18
  19. Uncle Pollo

    Uncle Pollo Long timer

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    Loose 20 pounds ... instant power to ratio gain.
    #19
  20. Uncle Pollo

    Uncle Pollo Long timer

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    Nah .... it does fine.


    I had cars that behaved worse.
    #20