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My experience dropping three (3) teeth on the rear sprocket.

Discussion in 'XJ Technical Chat' started by jtroto, Sep 19, 2013.

  1. jtroto

    jtroto New Member

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    Location:
    Lafayette, IN
    I have a 1982 xs400rj Seca with 8,000 Miles on it (yes 8,000). A little rusty but otherwise in very good condition. Recently had the carb tuned and synced. This is my first and only bike, aside from my Aprilia Scarabeo 50.

    Having said that, I had to replace the chain and sprockets. The bike had been left outside for many years, and there is a lot of rust still on it. So I decided to keep the front sprocket stock and drop a few teeth on the rear.

    Searching ebay, I found several steel 38 and 37 tooth sprockets, but I wanted a higher top-end. I found a 35 tooth rear sprocket on sale and jumped on it.

    First: gear ratios
    I originally was at a nearly 1:1 in 5th gear with 6th gear as an overdrive. (as I call it)

    Originally:
    Front Sprocket: 16 Tooth Steel Stock
    Rear Sprocket: 38 Tooth Steel Stock

    Change:
    Front Sprocket: 16 Tooth Steel (No Change)
    Rear Sprocket: 35 Tooth Aluminum

    Result:
    Originally: 50mph at 5000rpm in 5th gear
    55mph at 5000rpm in 6th gear
    Now: 54mph at 5000rpm in 5th gear
    60mph at 5000rpm in 6th gear

    ~5% increase in speed/gear. So, my highway cruising speed is much more comfortable. I find myself gripping the bike with my legs LESS and able to ride more upright as I go down the road at 60mph.

    Additionally, my mpg's increased from 55 to ~60.

    Yes, the acceleration decreased, but these 400's were not really speed demons to begin with, and I really like not having to shift through as many gear in town. There is no significant difference in first gear.

    I took a 180 mile trip over labor day, and everything worked fine. I really do enjoy the new gear ratios.

    In summary, I almost dropped a full gear (the old 6th gear now feels like 5th gear). This is easier on me in town and on the highway.

    My experience,
     
  2. Rayjay1959

    Rayjay1959 Member

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    Location:
    Prescott, az
    I like my shaft drive, but it would be nice to be able to change the gearing so easy. I'm a long distance cruiser, so the higher gear ratio's would work for me as well.
     
  3. pjk_xj700

    pjk_xj700 Member

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    Yeah, although I love the quiet-ness, clean-ness, and ease of the shaft drive, I sorely miss being able to change up gear ratios. I dropped 5 on the wife's tw200 and made it nice for riding on the road.
     
  4. cutlass79500

    cutlass79500 Well-Known Member

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    Only problem with a aluminum sprocket is they wear out very quickly usually in about 5k miles or so +or- keep it well lubed
     
  5. quebecois59

    quebecois59 Well-Known Member

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    Maybe my maths aren't good, but doesn't it make closer to a 9% increase (60 mph compared to 55mph before, a difference of 5 mph on 55 mph)?
     

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