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Nighthawk to get lower Sprockets

Discussion in 'Moto Club' started by J.R. Bob Dobbs, Feb 18, 2006.

  1. J.R. Bob Dobbs

    J.R. Bob Dobbs Nerd

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    After putting about 1000mi on my new 1995 CB750, I've decided it's geared a little too "high" for my taste.

    So, I ordered a set of sprockets (14F/39R) to replace the stockers (15F/38R). This will give me about 10% more RPM, and rear-wheel torque, in any given gear at all speeds. The pair of sprockets cost $61 delivered, from www.sprocketspecialists.com

    I've done final gear-ratio swaps in a car, and I think I know what to expect. The only cons I can think of are: reduced top speed (supposedly rpm limited to about 128mph stock, but I don't care about top speed), and reduced gas mileage.

    The sprockets are due to arrive Monday, I'll do the installation myself and road test it as soon as weather and work permits. I might just do the front at first, that will give about 7% more rather than 10%.
     
  2. Rosey

    Rosey

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    You may know this, but it's usually a good idea to replace sprockets and chains together. A worn chain will rapidly wear new sprockets and visa versa. If your current chain is in excellent condition, swap away!
     

  3. J.R. Bob Dobbs

    J.R. Bob Dobbs Nerd

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    Success! It was a straightforward install.

    The results are exactly as I expected, and it's about the best $61 I've spent. If you're experienced mechanically, it's an easy 2hr job, though I spent a little longer as I don't rush.

    RPM's are up exactly 10%, and there's significantly more pull in all gears. It's more controllable at low speed in 1st, less/no clutch slipping required, and 5th is more useful. The stock feeling of being geared too high is gone. Me likey!

    The front sprocket was US made, and is a very nice piece. The rear sprocket is Chinese, and the edges of the teeth needed some de-burring to remove sharp machining flash. I spent about an hour "finishing" the rear sprocket.

    The chain has very low miles so I didn't replace it.
     
  4. gixxer11

    gixxer11 bbrrraaapppppp!

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    A common mistake is to change sprokets with out checking the chain size. Lots of factory chains are 525 or 535. At first glance they look like they will work, take a closer look though, and you can see that they won't jive. A very expensive mistake! I'm sure you did it right, J.R. I was just pointing that out for other GTers, in case they didn't know.
     
  5. J.R. Bob Dobbs

    J.R. Bob Dobbs Nerd

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    Yes, my chain pitch matches both new sprockets.

    I'm surprised more folks don't tailor the gearing to their liking, considering how easy and inexpensive it is. Perhaps most bikes just don't feel as "overgeared" as mine did, the I4 does like to rev.

    For about the same money I could have gotten a K&N. No thank you!!!!
     
  6. fnfalman

    fnfalman Chicks Dig It

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    JR,

    Did you feel any significant increase in buzziness?
     
  7. J.R. Bob Dobbs

    J.R. Bob Dobbs Nerd

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    The motor starts getting "buzzy" just above 5000rpm. That hasn't changed.

    It gets buzzy in 5th around 70mph, before it was closer to 80. Though at that speed the wind pretty much completely overpowers the buzz. I really only notice it when winding it up in the lower gears, which hasn't changed, it just appears at a slightly lower mph in each gear.

    The buzz coincides with the powerband, so if you feel the buzz it's ready to scoot ;) The powerband surge starts around 5500rpm and builds steadily until redline (8600), it gets louder, buzzier, and pulls harder the higher it revs.


    I rode it about 2hrs today, the bike feels stronger everywhere, and also is more manageable in stop-and-go traffic.
     
  8. J.R. Bob Dobbs

    J.R. Bob Dobbs Nerd

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    I've run thru two tanks of gas since swapping the sprockets, and surprisingly my mileage hasn't changed. 43 before, 43 after.
     
  9. fnfalman

    fnfalman Chicks Dig It

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    You should count yourself lucky. My Tuono went from 38 to 35-MPH. And with the installation of the Power Commander and re-fuel mapping (hopefully this week), I'm sure that it'll go down closer to 30-MPH.;P
     
  10. J.R. Bob Dobbs

    J.R. Bob Dobbs Nerd

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    You're right, I can't explain why my mileage hasn't decreased. I do use 5th (top gear) more often than before the swap, but most of my time is still spent motoring around in 3rd or 4th.

    I don't ride the interstates, I live in the boonies. It does see redline a few times each ride, so I don't really baby it, though I generally ride conservatively and close to the speed limit, with occasional twists of the throttle where appropriate.

    I'm happy the MPG hasn't dropped, but would consider it a fine trade-off even if it does drop a few mpg. I'm **very** pleased with the results of the sprocket swap, it's quicker and more responsive from idle to redline.

    YMMV :) haha :)