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Thread: 1991 K 75 RT with 74 horse power ???

  1. #1

    1991 K 75 RT with 74 horse power ???

    I just noticed my 1991 K 75 is rated at 70 horse power at 8,500 rpms .
    My 1991 Harley softail with it's stock engine is rated at 48 horse power at around 5,500 rpm's .
    Of the 2 bikes the Harley seems to have more acceleration.. could it be the rpm's that make a difference in the ratings ?

  2. #2
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    Could it be the torque differences you're feeling? The K75 seems to have 50 ft-lbs of torque around 6700 RPM while the softtail has around 100 ft-lbs of torque at 3000 RPM. I'm not sure I have the right info on the Harley...difficult to find something definitive.
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    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Registered User
    Join Date
    Mar 2019
    Catskill MTS
    Torque on a stock EVO is around 65-70 lbs. The difference you are feeling is the Harley is shaking more and you thinks it going faster, the BMW is a lot smoother and you don't realize you are going a lot faster then you think. One way to do it is ride both bikes and don't look at the speedo until you thing you going at cruising speed.

  4. #4
    MOA #24991 Pauls1150's Avatar
    Join Date
    Apr 2008
    south of Los Angeles
    Several factors are involved...
    Bottom-end torque is what gets you off the line (also useful for pulling tree stumps and climbing walls with full bags). The Harley has a lot more low-end than a K75; the K is a "spinner" and has to rev up to make the HP.
    When people talk about power-to-weight ratio, they're usually referring to Horsepower - not "torquepower".
    Certainly the K weighs less, but "off the line", at lower revs, the power isn't there.
    Acceleration also involves gear ratio and flywheel effect - the HD has a heavier crank/flywheel assembly, and this makes it MUCH easier to just "drop the hammer" and git. It also has a clutch that is more tolerant to deliberate abuse, since the designers already knew about the low-rpm torque.
    My girlfriend found my FLH MUCH easier to ride than my K75.

  5. #5
    Dances With Sheep GREGFEELER's Avatar
    Join Date
    Mar 2003
    Boise, ID
    A mistake a lot of first time K75 owners make is to baby the engine. A K75 starts to make power above 5,500 RPM and up. Wind it up towards red line! You will not hurt the engine at all and you will be amazed at the additional power.
    Greg Feeler
    2022 BMW MOA "Wander Farther" Rally Co-Chair
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  6. #6
    3 Red Bricks
    Join Date
    Jan 2007
    Pleasanton, Ca.
    There is also a rev limiter to prevent over revving the engine.

    Ridden properly, the K75 is faster than the Harley.


    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

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